diff --git a/include/DFA/DFAGraph.hpp b/include/DFA/DFAGraph.hpp
index 82b5c5a..d410e9a 100644
--- a/include/DFA/DFAGraph.hpp
+++ b/include/DFA/DFAGraph.hpp
@@ -51,7 +51,8 @@ class DFAGraph {
   void RemoveFinalVertex(size_t number);
   void RemoveStartVertex(size_t number);
 
-  std::shared_ptr<Vertex> GetVertex(size_t number);
+  Vertex& GetVertex(size_t number);
+  bool NotExistVertex(size_t number);
 
   size_t GetCountVertexes() const;
   const std::vector<size_t>& GetFinalVertexes() const;
@@ -62,7 +63,7 @@ class DFAGraph {
   void CreateDotFile(const std::string& filename) const;
  private:
   size_t count_vertexes_ = 0;
-  std::map<size_t, std::shared_ptr<Vertex>> vertexes_;
+  std::map<size_t, Vertex> vertexes_;
   std::vector<size_t> final_vertexes_;
   std::vector<size_t> start_vertexes_;
 };
diff --git a/include/NFA/NFAGraph.hpp b/include/NFA/NFAGraph.hpp
index 69e1d45..6fd1738 100644
--- a/include/NFA/NFAGraph.hpp
+++ b/include/NFA/NFAGraph.hpp
@@ -55,7 +55,9 @@ class NFAGraph {
                    std::vector<size_t> start_vertexes,
                    std::vector<size_t> final_vertexes);
 
-  std::shared_ptr<Vertex> GetVertex(size_t number);
+  Vertex& GetVertex(size_t number);
+  bool NotExistVertex(size_t number);
+
   size_t GetCountVertexes() const;
   const std::vector<size_t>& GetFinalVertexes() const;
   const std::vector<size_t>& GetStartVertexes() const;
@@ -64,7 +66,7 @@ class NFAGraph {
   void CreateDotFile(const std::string& filename) const;
  private:
   size_t count_vertexes_ = 0;
-  std::map<size_t, std::shared_ptr<Vertex>> vertexes_;
+  std::map<size_t, Vertex> vertexes_;
   std::vector<size_t> final_vertexes_;
   std::vector<size_t> start_vertexes_;
 };
diff --git a/src/DFA/DFAGraph.cpp b/src/DFA/DFAGraph.cpp
index 05378b3..3742ec0 100644
--- a/src/DFA/DFAGraph.cpp
+++ b/src/DFA/DFAGraph.cpp
@@ -11,9 +11,9 @@ DFAGraph::DFAGraph(DFAGraph&& another) {
   std::swap(start_vertexes_, another.start_vertexes_);
 
   for (auto& i: vertexes_)
-    i.second->owner_ = this;
+    i.second.owner_ = this;
   for (auto& i: another.vertexes_)
-    i.second->owner_ = &another;
+    i.second.owner_ = &another;
 }
 
 DFAGraph& DFAGraph::operator=(DFAGraph&& another) {
@@ -23,27 +23,27 @@ DFAGraph& DFAGraph::operator=(DFAGraph&& another) {
   std::swap(start_vertexes_, another.start_vertexes_);
 
   for (auto& i: vertexes_)
-    i.second->owner_ = this;
+    i.second.owner_ = this;
   for (auto& i: another.vertexes_)
-    i.second->owner_ = &another;
+    i.second.owner_ = &another;
   return *this;
 }
 size_t DFAGraph::AddNewVertex() {
-  vertexes_[count_vertexes_] = std::make_shared<Vertex>(this);
-  vertexes_[count_vertexes_]->number_ = count_vertexes_;
+  vertexes_.emplace(count_vertexes_, this);
+  GetVertex(count_vertexes_).number_ = count_vertexes_;
   return count_vertexes_++;
 }
 
 void DFAGraph::AddFinalVertex(size_t number) {
-  if (!vertexes_[number]->is_final_) {
-    vertexes_[number]->is_final_ = true;
+  if (!GetVertex(number).is_final_) {
+    GetVertex(number).is_final_ = true;
     final_vertexes_.push_back(number);
   }
 }
 
 void DFAGraph::AddStartVertex(size_t number) {
-  if (!vertexes_[number]->is_start_) {
-    vertexes_[number]->is_start_ = true;
+  if (!GetVertex(number).is_start_) {
+    GetVertex(number).is_start_ = true;
     start_vertexes_.push_back(number);
   }
 }
@@ -58,7 +58,7 @@ void DFAGraph::RemoveVertex(size_t number) {
 void DFAGraph::RemoveFinalVertex(size_t number) {
   for (size_t i = 0; i < final_vertexes_.size(); ++i) {
     if (final_vertexes_[i] == number) {
-      vertexes_[number]->is_final_ = false;
+      GetVertex(number).is_final_ = false;
       std::swap(final_vertexes_[i], final_vertexes_.back());
       final_vertexes_.pop_back();
       break;
@@ -69,7 +69,7 @@ void DFAGraph::RemoveFinalVertex(size_t number) {
 void DFAGraph::RemoveStartVertex(size_t number) {
   for (size_t i = 0; i < start_vertexes_.size(); ++i) {
     if (start_vertexes_[i] == number) {
-      vertexes_[number]->is_start_ = false;
+      GetVertex(number).is_start_ = false;
       std::swap(start_vertexes_[i], start_vertexes_.back());
       start_vertexes_.pop_back();
       break;
@@ -77,10 +77,14 @@ void DFAGraph::RemoveStartVertex(size_t number) {
   }
 }
 
-std::shared_ptr<DFAGraph::Vertex> DFAGraph::GetVertex(size_t number) {
-  if (vertexes_.count(number))
-    return vertexes_[number];
-  return nullptr;
+DFAGraph::Vertex& DFAGraph::GetVertex(size_t number) {
+  if (!NotExistVertex(number))
+    return vertexes_.at(number);
+  throw std::out_of_range("This vertex don't exist");
+}
+
+bool DFAGraph::NotExistVertex(size_t number) {
+  return !vertexes_.count(number);
 }
 
 size_t DFAGraph::GetCountVertexes() const {
@@ -97,12 +101,12 @@ const std::vector<size_t>& DFAGraph::GetStartVertexes() const {
 
 void DFAGraph::Print() const {
   for (auto i: vertexes_) {
-    std::cout << i.second->number_ << " " << "f-" << i.second->is_final_ << " s-" <<
-        i.second->is_start_ << std::endl;
+    std::cout << i.second.number_ << " " << "f-" << i.second.is_final_ << " s-" <<
+        i.second.is_start_ << std::endl;
   }
   for (auto& i: vertexes_) {
-    for (auto& j: i.second->transitions_) {
-      std::cout << i.second->number_ << "->" << j.second << " <" << j.first << ">" <<
+    for (auto& j: i.second.transitions_) {
+      std::cout << i.second.number_ << "->" << j.second << " <" << j.first << ">" <<
           std::endl;
     }
   }
@@ -110,35 +114,35 @@ void DFAGraph::Print() const {
 }
 
 bool DFAGraph::Accepted(const std::string& str) const {
-  std::shared_ptr<const Vertex> current = vertexes_.at(start_vertexes_[0]);
+  size_t current = vertexes_.at(start_vertexes_[0]).GetNumber();
   for (auto i: str) {
-    if (current->GetTransitions().count(i)) {
-      current = vertexes_.at(current->GetTransitions().at(i));
+    if (vertexes_.at(current).GetTransitions().count(i)) {
+      current = vertexes_.at(vertexes_.at(current).GetTransitions().at(i)).GetNumber();
     } else {
       return false;
     }
   }
-  return current->IsFinal();
+  return vertexes_.at(current).IsFinal();
 }
+
 void DFAGraph::CreateDotFile(const std::string& filename) const {
   std::ofstream out(filename);
   out << "digraph G {\n";
 
   for (auto& i: vertexes_) {
-    for (auto& j: i.second->transitions_) {
-      out << i.first << "->" << j.second << "[label=" << j.first << "]\n";
+    for (auto& j: i.second.transitions_) {
+      out << i.first << "." << j.second << "[label=" << j.first << "]\n";
     }
-    if (i.second->IsStart() && i.second->IsFinal()) {
+    if (i.second.IsStart() && i.second.IsFinal()) {
       out << "  " << i.first << " [shape=star];\n";
-    } else if (i.second->IsStart()) {
+    } else if (i.second.IsStart()) {
       out << "  " << i.first << " [shape=rarrow];\n";
-    } else if (i.second->IsFinal()) {
+    } else if (i.second.IsFinal()) {
       out << "  " << i.first << " [shape=Msquare];\n";
     }
   }
 
   out << "}\n";
-
 }
 }
 
diff --git a/src/DFA/DFAGraphVertex.cpp b/src/DFA/DFAGraphVertex.cpp
index 015ba92..b1602c8 100644
--- a/src/DFA/DFAGraphVertex.cpp
+++ b/src/DFA/DFAGraphVertex.cpp
@@ -26,11 +26,11 @@ const std::map<char, size_t>& Vertex::GetBackTransitions() const {
 
 void Vertex::AddEdge(char symbol, size_t number) {
   transitions_[symbol] = number;
-  owner_->GetVertex(number)->back_transitions_[symbol] = number_;
+  owner_->GetVertex(number).back_transitions_[symbol] = number_;
 }
 
 void Vertex::RemoveEdge(char symbol) {
-  owner_->GetVertex(transitions_[symbol])->back_transitions_.erase(symbol);
+  owner_->GetVertex(transitions_[symbol]).back_transitions_.erase(symbol);
   transitions_.erase(symbol);
 }
 
diff --git a/src/NFA/NFAGraph.cpp b/src/NFA/NFAGraph.cpp
index ade1e57..b27bb21 100644
--- a/src/NFA/NFAGraph.cpp
+++ b/src/NFA/NFAGraph.cpp
@@ -11,9 +11,9 @@ NFAGraph::NFAGraph(NFAGraph&& another) {
   std::swap(start_vertexes_, another.start_vertexes_);
 
   for (auto& i: vertexes_)
-    i.second->owner_ = this;
+    i.second.owner_ = this;
   for (auto& i: another.vertexes_)
-    i.second->owner_ = &another;
+    i.second.owner_ = &another;
 }
 
 NFAGraph& NFAGraph::operator=(NFAGraph&& another) {
@@ -23,28 +23,28 @@ NFAGraph& NFAGraph::operator=(NFAGraph&& another) {
   std::swap(start_vertexes_, another.start_vertexes_);
 
   for (auto& i: vertexes_)
-    i.second->owner_ = this;
+    i.second.owner_ = this;
   for (auto& i: another.vertexes_)
-    i.second->owner_ = &another;
+    i.second.owner_ = &another;
   return *this;
 }
 
 size_t NFAGraph::AddNewVertex() {
-  vertexes_[count_vertexes_] = std::make_shared<Vertex>(this);
-  vertexes_[count_vertexes_]->number_ = count_vertexes_;
+  vertexes_.emplace(count_vertexes_, this);
+  GetVertex(count_vertexes_).number_ = count_vertexes_;
   return count_vertexes_++;
 }
 
 void NFAGraph::AddFinalVertex(size_t number) {
-  if (!vertexes_[number]->is_final_) {
-    vertexes_[number]->is_final_ = true;
+  if (!GetVertex(number).is_final_) {
+    GetVertex(number).is_final_ = true;
     final_vertexes_.push_back(number);
   }
 }
 
 void NFAGraph::AddStartVertex(size_t number) {
-  if (!vertexes_[number]->is_start_) {
-    vertexes_[number]->is_start_ = true;
+  if (!GetVertex(number).is_start_) {
+    GetVertex(number).is_start_ = true;
     start_vertexes_.push_back(number);
   }
 }
@@ -58,7 +58,7 @@ void NFAGraph::RemoveVertex(size_t number) {
 void NFAGraph::RemoveFinalVertex(size_t number) {
   for (size_t i = 0; i < final_vertexes_.size(); ++i) {
     if (final_vertexes_[i] == number) {
-      vertexes_[number]->is_final_ = false;
+      GetVertex(number).is_final_ = false;
       std::swap(final_vertexes_[i], final_vertexes_.back());
       final_vertexes_.pop_back();
       break;
@@ -69,7 +69,7 @@ void NFAGraph::RemoveFinalVertex(size_t number) {
 void NFAGraph::RemoveStartVertex(size_t number) {
   for (size_t i = 0; i < start_vertexes_.size(); ++i) {
     if (start_vertexes_[i] == number) {
-      vertexes_[number]->is_start_ = false;
+      GetVertex(number).is_start_ = false;
       std::swap(start_vertexes_[i], start_vertexes_.back());
       start_vertexes_.pop_back();
       break;
@@ -87,24 +87,24 @@ void NFAGraph::Composition(NFAGraph&& nfa_graph,
 
   for (auto& i: nfa_graph.vertexes_) {
     new_count_vertexes = std::max(new_count_vertexes, i.first + count_vertexes_ + 1);
-    i.second->number_ += count_vertexes_;
+    i.second.number_ += count_vertexes_;
     std::map<char, std::set<size_t>> new_transitions;
-    for (auto& j: i.second->transitions_) {
+    for (auto& j: i.second.transitions_) {
       for (auto& k: j.second) {
         new_transitions[j.first].insert(k + count_vertexes_);
       }
     }
     std::map<char, std::set<size_t>> new_back_transitions;
-    for (auto& j: i.second->back_transitions_) {
+    for (auto& j: i.second.back_transitions_) {
       for (auto& k: j.second) {
         new_back_transitions[j.first].insert(k + count_vertexes_);
       }
     }
-    i.second->transitions_ = std::move(new_transitions);
-    i.second->back_transitions_ = std::move(new_back_transitions);
+    i.second.transitions_ = std::move(new_transitions);
+    i.second.back_transitions_ = std::move(new_back_transitions);
 
-    i.second->SetOwner(this);
-    vertexes_[i.second->number_] = std::move(i.second);
+    i.second.SetOwner(this);
+    vertexes_.emplace(i.second.number_, std::move(i.second));
   }
 
   for (auto& i: add_start_vertexes) {
@@ -118,28 +118,32 @@ void NFAGraph::Composition(NFAGraph&& nfa_graph,
 
   for (auto& i: start_vertexes) {
     for (auto& j: add_start_vertexes) {
-      vertexes_[i]->transitions_[' '].insert(j);
-      vertexes_[j]->back_transitions_[' '].insert(i);
+      GetVertex(i).transitions_[' '].insert(j);
+      GetVertex(j).back_transitions_[' '].insert(i);
     }
   }
   for (auto& i: add_final_vertexes) {
     for (auto& j: final_vertexes) {
-      vertexes_[i]->transitions_[' '].insert(j);
-      vertexes_[j]->back_transitions_[' '].insert(i);
+      GetVertex(i).transitions_[' '].insert(j);
+      GetVertex(j).back_transitions_[' '].insert(i);
     }
   }
   for (auto& i: add_final_vertexes) {
-    vertexes_[i]->is_final_ = false;
+    GetVertex(i).is_final_ = false;
   }
   for (auto& i: add_start_vertexes) {
-    vertexes_[i]->is_start_ = false;
+    GetVertex(i).is_start_ = false;
   }
 }
 
-std::shared_ptr<NFAGraph::Vertex> NFAGraph::GetVertex(size_t number) {
-  if (vertexes_.count(number))
-    return vertexes_[number];
-  return nullptr;
+NFAGraph::Vertex& NFAGraph::GetVertex(size_t number) {
+  if (!NotExistVertex(number))
+    return vertexes_.at(number);
+  throw std::out_of_range("This vertex don't exist");
+}
+
+bool NFAGraph::NotExistVertex(size_t number) {
+  return !vertexes_.count(number);
 }
 
 size_t NFAGraph::GetCountVertexes() const {
@@ -156,13 +160,13 @@ const std::vector<size_t>& NFAGraph::GetStartVertexes() const {
 
 void NFAGraph::Print() const {
   for (auto i: vertexes_) {
-    std::cout << i.second->number_ << " " << "f-" << i.second->is_final_ << " s-" <<
-        i.second->is_start_ << std::endl;
+    std::cout << i.second.number_ << " " << "f-" << i.second.is_final_ << " s-" <<
+        i.second.is_start_ << std::endl;
   }
   for (auto& i: vertexes_) {
-    for (auto& j: i.second->transitions_) {
+    for (auto& j: i.second.transitions_) {
       for (auto k: j.second) {
-        std::cout << i.second->number_ << "->" << k << " <" << j.first << ">" <<
+        std::cout << i.second.number_ << "." << k << " <" << j.first << ">" <<
             std::endl;
       }   
     }
@@ -175,16 +179,16 @@ void NFAGraph::CreateDotFile(const std::string& filename) const {
   out << "digraph G {\n";
 
   for (auto& i: vertexes_) {
-    for (auto& j: i.second->transitions_) {
+    for (auto& j: i.second.transitions_) {
       for (auto& k: j.second) {
-        out << i.first << "->" << k << "[label=" << j.first << "]\n";
+        out << i.first << "." << k << "[label=" << j.first << "]\n";
       }
     }
-    if (i.second->IsStart() && i.second->IsFinal()) {
+    if (i.second.IsStart() && i.second.IsFinal()) {
       out << "  " << i.first << " [shape=Mstar];\n";
-    } else if (i.second->IsStart()) {
+    } else if (i.second.IsStart()) {
       out << "  " << i.first << " [shape=Mdiamond];\n";
-    } else if (i.second->IsFinal()) {
+    } else if (i.second.IsFinal()) {
       out << "  " << i.first << " [shape=Msquare];\n";
     }
   }
diff --git a/src/NFA/NFAGraphVertex.cpp b/src/NFA/NFAGraphVertex.cpp
index a887fae..32610a9 100644
--- a/src/NFA/NFAGraphVertex.cpp
+++ b/src/NFA/NFAGraphVertex.cpp
@@ -26,17 +26,17 @@ const std::map<char, std::set<size_t>>& Vertex::GetBackTransitions() const {
 
 void Vertex::AddEdge(char symbol, size_t number) {
   transitions_[symbol].insert(number);
-  owner_->GetVertex(number)->back_transitions_[symbol];
-  owner_->GetVertex(number)->back_transitions_[symbol].insert(number_);
+  owner_->GetVertex(number).back_transitions_[symbol];
+  owner_->GetVertex(number).back_transitions_[symbol].insert(number_);
 }
 
 void Vertex::RemoveEdge(char symbol, size_t number) {
   transitions_[symbol].erase(number);
   if (transitions_[symbol].size() == 0)
     transitions_.erase(symbol);
-  owner_->GetVertex(number)->back_transitions_[symbol].erase(number_);
-  if (owner_->GetVertex(number)->back_transitions_[symbol].size() == 0)
-    owner_->GetVertex(number)->back_transitions_.erase(symbol);
+  owner_->GetVertex(number).back_transitions_[symbol].erase(number_);
+  if (owner_->GetVertex(number).back_transitions_[symbol].size() == 0)
+    owner_->GetVertex(number).back_transitions_.erase(symbol);
 }
 
 void Vertex::SetOwner(NFAGraph* owner) {
diff --git a/src/converters/DFAToFDFA.cpp b/src/converters/DFAToFDFA.cpp
index 8120746..6b7245d 100644
--- a/src/converters/DFAToFDFA.cpp
+++ b/src/converters/DFAToFDFA.cpp
@@ -6,38 +6,38 @@ DFAGraph DFAGraphToFDFAGraph(DFAGraph&& graph, const std::vector<char>& alphabet
   const int n = graph.GetCountVertexes();
   std::map<size_t, size_t> number_vertex_in_DFA;
   for (int i = 0; i < n; ++i) {
-    if (!graph.GetVertex(i)) continue;
+    if (graph.NotExistVertex(i)) continue;
     number_vertex_in_DFA[i] = result.AddNewVertex();
   }
   for (int i = 0; i < n; ++i) {
-    if (!graph.GetVertex(i)) continue;
-    if (graph.GetVertex(i)->IsFinal())
-      result.GetVertex(number_vertex_in_DFA[i])->SetFinal(true);
-    if (graph.GetVertex(i)->IsStart())
-      result.GetVertex(number_vertex_in_DFA[i])->SetStart(true);
+    if (graph.NotExistVertex(i)) continue;
+    if (graph.GetVertex(i).IsFinal())
+      result.GetVertex(number_vertex_in_DFA[i]).SetFinal(true);
+    if (graph.GetVertex(i).IsStart())
+      result.GetVertex(number_vertex_in_DFA[i]).SetStart(true);
 
-    const auto& transitions = graph.GetVertex(i)->GetTransitions();
+    const auto& transitions = graph.GetVertex(i).GetTransitions();
     for (const auto& t: transitions) {
-      result.GetVertex(number_vertex_in_DFA[i])->AddEdge(t.first, t.second);      
+      result.GetVertex(number_vertex_in_DFA[i]).AddEdge(t.first, t.second);
     }
   }
 
   size_t drain = result.AddNewVertex();
 
   for (int i = 0; i < n; ++i) {
-    const auto& transitions = graph.GetVertex(i)->GetTransitions();
+    const auto& transitions = graph.GetVertex(i).GetTransitions();
     for (char j: alphabet) {
       if (!transitions.count(j)) {
-        result.GetVertex(i)->AddEdge(j, drain);
+        result.GetVertex(i).AddEdge(j, drain);
       }
     }
   }
 
-  if (result.GetVertex(drain)->GetBackTransitions().size() == 0) {
+  if (result.GetVertex(drain).GetBackTransitions().size() == 0) {
     result.RemoveVertex(drain);
   } else {
     for (char j: alphabet) {
-      result.GetVertex(drain)->AddEdge(j, drain);
+      result.GetVertex(drain).AddEdge(j, drain);
     }
   }
 
diff --git a/src/converters/DFAToMinDFA.cpp b/src/converters/DFAToMinDFA.cpp
index 5372265..591e49e 100644
--- a/src/converters/DFAToMinDFA.cpp
+++ b/src/converters/DFAToMinDFA.cpp
@@ -11,8 +11,8 @@ DFAGraph DFAGraphToMinDFAGraph(DFAGraph&& graph) {
   {
     std::set<char> set_alphabet;
     for (int i = 0; i < n; ++i) {
-      if (!graph.GetVertex(i)) continue;
-      for (auto i: graph.GetVertex(i)->GetTransitions()) {
+      if (graph.NotExistVertex(i)) continue;
+      for (auto i: graph.GetVertex(i).GetTransitions()) {
         set_alphabet.insert(i.first);
       }
     }
@@ -25,11 +25,11 @@ DFAGraph DFAGraphToMinDFAGraph(DFAGraph&& graph) {
   {
     std::vector<std::vector<size_t>>& layer(table[0]);
     for (int i = 0; i < n; ++i) {
-      layer[i][0] = graph.GetVertex(i)->IsFinal();
+      layer[i][0] = graph.GetVertex(i).IsFinal();
     }
     for (int i = 0; i < n; ++i) {
       for (int j = 0; j < alphabet.size(); ++j) {
-        const auto& transitions = graph.GetVertex(i)->GetTransitions();
+        const auto& transitions = graph.GetVertex(i).GetTransitions();
         if (transitions.count(alphabet[j]))
           layer[i][j + 1] = layer[transitions.at(alphabet[j])][0];
         else
@@ -57,7 +57,7 @@ DFAGraph DFAGraphToMinDFAGraph(DFAGraph&& graph) {
     }
     for (int i = 0; i < n; ++i) {
       for (int j = 0; j < alphabet.size(); ++j) {
-        const auto& transitions = graph.GetVertex(i)->GetTransitions();
+        const auto& transitions = graph.GetVertex(i).GetTransitions();
         if (transitions.count(alphabet[j]))
           layer[i][j + 1] = layer[transitions.at(alphabet[j])][0];
         else
@@ -92,16 +92,16 @@ DFAGraph DFAGraphToMinDFAGraph(DFAGraph&& graph) {
   for (int i = 0; i < n; ++i) {
     size_t v = number_vertex_in_DFA[last_layer[i][0]];
 
-    const auto& transitions = graph.GetVertex(i)->GetTransitions();
+    const auto& transitions = graph.GetVertex(i).GetTransitions();
     for (const auto& t: transitions) {
       if (last_layer[t.second][0] != -1LL) {
         size_t u = number_vertex_in_DFA[last_layer[t.second][0]];
-        result.GetVertex(v)->AddEdge(t.first, u);      
+        result.GetVertex(v).AddEdge(t.first, u);
       } 
     }
 
-    if (graph.GetVertex(i)->IsStart()) result.GetVertex(v)->SetStart(true);
-    if (graph.GetVertex(i)->IsFinal()) result.GetVertex(v)->SetFinal(true);
+    if (graph.GetVertex(i).IsStart()) result.GetVertex(v).SetStart(true);
+    if (graph.GetVertex(i).IsFinal()) result.GetVertex(v).SetFinal(true);
   }
 
   return result;
diff --git a/src/converters/DFAToRegular.cpp b/src/converters/DFAToRegular.cpp
index 4a59507..ffd6f0c 100644
--- a/src/converters/DFAToRegular.cpp
+++ b/src/converters/DFAToRegular.cpp
@@ -12,8 +12,8 @@ std::string DFAGraphToRegular(DFAGraph&& graph) {
   size_t start = -1;
 
   for (int i = 0; i < n - 1; ++i) {
-    if (!graph.GetVertex(i)) continue;
-    if (graph.GetVertex(i)->IsStart()) start = i;
+    if (graph.NotExistVertex(i)) continue;
+    if (graph.GetVertex(i).IsStart()) start = i;
   }
 
   rename[start] = 1;
@@ -26,13 +26,13 @@ std::string DFAGraphToRegular(DFAGraph&& graph) {
 
 
   for (int i = 0; i < n - 1; ++i) {
-    if (!graph.GetVertex(i)) continue;
-    const auto& vertex_transitions = graph.GetVertex(i)->GetTransitions();
+    if (graph.NotExistVertex(i)) continue;
+    const auto& vertex_transitions = graph.GetVertex(i).GetTransitions();
 
     for (auto j: vertex_transitions) {
       transitions[rename[i]][rename[j.second]].insert(std::string(1, j.first));
     }
-    if (graph.GetVertex(i)->IsFinal()) {
+    if (graph.GetVertex(i).IsFinal()) {
       transitions[rename[i]][0].insert("( )");
     }
   }
@@ -99,7 +99,7 @@ std::string DFAGraphToRegular(DFAGraph&& graph) {
   std::string begin_to_end;
 
   if (transitions[1][1].size() != 0) {
-    for (const std::string s: transitions[1][1]) {
+    for (const std::string& s: transitions[1][1]) {
       loop += "(";
       loop += s;
       loop += ")";
@@ -109,7 +109,7 @@ std::string DFAGraphToRegular(DFAGraph&& graph) {
       loop.pop_back();
     loop = "(" + loop + ")*";
   }
-  for (const std::string s: transitions[1][0]) {
+  for (const std::string& s: transitions[1][0]) {
     begin_to_end += "(";
     begin_to_end += s;
     begin_to_end += ")";
diff --git a/src/converters/InvertFDFA.cpp b/src/converters/InvertFDFA.cpp
index 4d3c5e0..61ad9e2 100644
--- a/src/converters/InvertFDFA.cpp
+++ b/src/converters/InvertFDFA.cpp
@@ -4,8 +4,8 @@ namespace converters {
 DFAGraph InvertFDFAGraph(DFAGraph&& fdfa_graph) {
   const size_t n = fdfa_graph.GetCountVertexes();
   for (int i = 0; i < n; ++i) {
-    if (!fdfa_graph.GetVertex(i)) continue;
-    fdfa_graph.GetVertex(i)->SetFinal(!fdfa_graph.GetVertex(i)->IsFinal());
+    if (fdfa_graph.NotExistVertex(i)) continue;
+    fdfa_graph.GetVertex(i).SetFinal(fdfa_graph.GetVertex(i).IsFinal());
   }
   return std::move(fdfa_graph);
 }
diff --git a/src/converters/NFAToDFA.cpp b/src/converters/NFAToDFA.cpp
index 29e2df6..fe24976 100644
--- a/src/converters/NFAToDFA.cpp
+++ b/src/converters/NFAToDFA.cpp
@@ -10,13 +10,13 @@ NFAGraph AddAllEpsilonTransitions(NFAGraph&& nfa_graph) {
 
   std::function<void(int, int)> dfs = [&nfa_graph, &used, &dfs](int u, int v) -> void {
     used[v] = true;
-    const auto& transitions = nfa_graph.GetVertex(v)->GetTransitions();
+    const auto& transitions = nfa_graph.GetVertex(v).GetTransitions();
     if (transitions.count(' ')) {
       const auto& s = transitions.at(' ');
       for (auto i: s) {
         if (!used[i]) {
           if (u != i)
-            nfa_graph.GetVertex(u)->AddEdge(' ', i);
+            nfa_graph.GetVertex(u).AddEdge(' ', i);
           dfs(u, i);
         }
       }
@@ -24,7 +24,7 @@ NFAGraph AddAllEpsilonTransitions(NFAGraph&& nfa_graph) {
   };
 
   for (int i = 0; i < n; ++i) {
-    if (!nfa_graph.GetVertex(i)) continue;
+    if (nfa_graph.NotExistVertex(i)) continue;
 
     used.assign(n, false);
     dfs(i, i);
@@ -36,15 +36,15 @@ NFAGraph AddAllPossibleStartFinal(NFAGraph&& nfa_graph) {
   if (nfa_graph.GetStartVertexes().size() != 1) {
     size_t start_vertex = nfa_graph.AddNewVertex();
     for (auto v: nfa_graph.GetStartVertexes()) {
-      nfa_graph.GetVertex(start_vertex)->AddEdge(' ', v);
+      nfa_graph.GetVertex(start_vertex).AddEdge(' ', v);
     }
   }
   for (const auto& v: nfa_graph.GetFinalVertexes()) {
-    const auto& transitions = nfa_graph.GetVertex(v)->GetBackTransitions();
+    const auto& transitions = nfa_graph.GetVertex(v).GetBackTransitions();
     if (transitions.count(' ')) {
       const auto& s = transitions.at(' ');
       for (auto i: s) {
-        nfa_graph.GetVertex(i)->SetFinal(true);
+        nfa_graph.GetVertex(i).SetFinal(true);
       }
     } 
   }
@@ -55,21 +55,21 @@ NFAGraph DeleteEpsilonTransitions(NFAGraph&& nfa_graph) {
   const int n = nfa_graph.GetCountVertexes();
 
   for (int v = 0; v < n; ++v) {
-    if (!nfa_graph.GetVertex(v)) continue;
+    if (nfa_graph.NotExistVertex(v)) continue;
 
-    const auto& transitions = nfa_graph.GetVertex(v)->GetTransitions();
+    const auto& transitions = nfa_graph.GetVertex(v).GetTransitions();
     if (transitions.count(' ')) {
       auto s = transitions.at(' ');
       for (auto u: s) {
-        for (auto& i: nfa_graph.GetVertex(u)->GetTransitions()) {
+        for (auto& i: nfa_graph.GetVertex(u).GetTransitions()) {
           if (i.first == ' ') continue;
           for (auto t: i.second) {
-            nfa_graph.GetVertex(v)->AddEdge(i.first, t);
+            nfa_graph.GetVertex(v).AddEdge(i.first, t);
           } 
         }
       }
       for (auto u: s) {
-        nfa_graph.GetVertex(v)->RemoveEdge(' ', u);
+        nfa_graph.GetVertex(v).RemoveEdge(' ', u);
       }   
     }
   }
@@ -87,8 +87,8 @@ NFAGraph DeleteTransitionsByOneLetter(NFAGraph&& nfa_graph) {
 
   std::set<char> alphabet;
   for (int i = 0; i < n; ++i) {
-    if (!nfa_graph.GetVertex(i)) continue;
-    for (const auto& j: nfa_graph.GetVertex(i)->GetTransitions()) {
+    if (nfa_graph.NotExistVertex(i)) continue;
+    for (const auto& j: nfa_graph.GetVertex(i).GetTransitions()) {
       if (j.second.size() > 0)
         alphabet.insert(j.first);
     }
@@ -106,7 +106,7 @@ NFAGraph DeleteTransitionsByOneLetter(NFAGraph&& nfa_graph) {
     for (auto symbol: alphabet) {
       std::set<size_t> result;
       for (auto v: current) {
-        const auto& transitions = nfa_graph.GetVertex(v)->GetTransitions();
+        const auto& transitions = nfa_graph.GetVertex(v).GetTransitions();
         if (transitions.count(symbol)) {
           const auto& s = transitions.at(symbol);
           result.insert(s.begin(), s.end());
@@ -127,7 +127,7 @@ NFAGraph DeleteTransitionsByOneLetter(NFAGraph&& nfa_graph) {
     int v = number_vertex_in_result_tree[i.first.first];
     int u = number_vertex_in_result_tree[i.second];
     char symbol = i.first.second;
-    result_tree.GetVertex(v)->AddEdge(symbol, u);
+    result_tree.GetVertex(v).AddEdge(symbol, u);
   }
 
   for (auto i: number_vertex_in_result_tree) {
@@ -135,10 +135,10 @@ NFAGraph DeleteTransitionsByOneLetter(NFAGraph&& nfa_graph) {
     auto v = i.second;
 
     for (auto i: s) {
-      if (nfa_graph.GetVertex(i)->IsFinal())
-        result_tree.GetVertex(v)->SetFinal(true);
-      if (nfa_graph.GetVertex(i)->IsStart())
-        result_tree.GetVertex(v)->SetStart(true);
+      if (nfa_graph.GetVertex(i).IsFinal())
+        result_tree.GetVertex(v).SetFinal(true);
+      if (nfa_graph.GetVertex(i).IsStart())
+        result_tree.GetVertex(v).SetStart(true);
     }
   }
 
@@ -146,6 +146,7 @@ NFAGraph DeleteTransitionsByOneLetter(NFAGraph&& nfa_graph) {
 }
 
 DFAGraph NFAGraphToDFAGraph(NFAGraph&& nfa_graph) {
+  nfa_graph = AddAllEpsilonTransitions(std::move(nfa_graph));
   nfa_graph = DeleteTransitionsByOneLetter(DeleteEpsilonTransitions(AddAllPossibleStartFinal(
       AddAllEpsilonTransitions(std::move(nfa_graph)))));
 
@@ -153,20 +154,20 @@ DFAGraph NFAGraphToDFAGraph(NFAGraph&& nfa_graph) {
   DFAGraph result;
   std::map<int, int> number_vertex_in_DFA;
   for (int i = 0; i < n; ++i) {
-    if (!nfa_graph.GetVertex(i)) continue;
+    if (nfa_graph.NotExistVertex(i)) continue;
     number_vertex_in_DFA[i] = result.AddNewVertex();
   }
   for (int i = 0; i < n; ++i) {
-    if (!nfa_graph.GetVertex(i)) continue;
-    if (nfa_graph.GetVertex(i)->IsFinal())
-      result.GetVertex(number_vertex_in_DFA[i])->SetFinal(true);
-    if (nfa_graph.GetVertex(i)->IsStart())
-      result.GetVertex(number_vertex_in_DFA[i])->SetStart(true);
+    if (nfa_graph.NotExistVertex(i)) continue;
+    if (nfa_graph.GetVertex(i).IsFinal())
+      result.GetVertex(number_vertex_in_DFA[i]).SetFinal(true);
+    if (nfa_graph.GetVertex(i).IsStart())
+      result.GetVertex(number_vertex_in_DFA[i]).SetStart(true);
 
-    const auto& transitions = nfa_graph.GetVertex(i)->GetTransitions();
+    const auto& transitions = nfa_graph.GetVertex(i).GetTransitions();
     for (const auto& t: transitions) {
       if (t.second.size() != 1) throw std::logic_error("");
-      result.GetVertex(number_vertex_in_DFA[i])->AddEdge(t.first, *t.second.begin());      
+      result.GetVertex(number_vertex_in_DFA[i]).AddEdge(t.first, *t.second.begin());
     }
   }
   return result;
diff --git a/src/converters/RegularToNFA.cpp b/src/converters/RegularToNFA.cpp
index c08b686..acae0a6 100644
--- a/src/converters/RegularToNFA.cpp
+++ b/src/converters/RegularToNFA.cpp
@@ -20,14 +20,14 @@ NFAGraph RegularToNFA(std::unique_ptr<Node, deleter> node) {
     result.AddStartVertex(end);
     for (char i: node->word) {
       auto tmp = result.AddNewVertex();
-      result.GetVertex(end)->AddEdge(i, tmp);
+      result.GetVertex(end).AddEdge(i, tmp);
       end = tmp;
     }
     if (node->modifier == Node::Modifier::Plus) {
-      result.GetVertex(end)->AddEdge(' ', start);
+      result.GetVertex(end).AddEdge(' ', start);
     } else if (node->modifier == Node::Modifier::Star) {
-      result.GetVertex(end)->AddEdge(' ', start);
-      result.GetVertex(start)->AddEdge(' ', end);
+      result.GetVertex(end).AddEdge(' ', start);
+      result.GetVertex(start).AddEdge(' ', end);
     }
     result.AddFinalVertex(end);
   } else if (node->type == Node::Type::Concatenation) {
@@ -47,14 +47,14 @@ NFAGraph RegularToNFA(std::unique_ptr<Node, deleter> node) {
     if (node->modifier == Node::Modifier::Plus) {
       for (auto start: start_vertexes) {
         for (auto end: end_vertexes) {
-          result.GetVertex(end)->AddEdge(' ', start);
+          result.GetVertex(end).AddEdge(' ', start);
         } 
       } 
     } else if (node->modifier == Node::Modifier::Star) {
       for (auto start: start_vertexes) {
         for (auto end: end_vertexes) {
-          result.GetVertex(end)->AddEdge(' ', start);
-          result.GetVertex(start)->AddEdge(' ', end);
+          result.GetVertex(end).AddEdge(' ', start);
+          result.GetVertex(start).AddEdge(' ', end);
         } 
       } 
     }
@@ -69,10 +69,10 @@ NFAGraph RegularToNFA(std::unique_ptr<Node, deleter> node) {
       result.Composition(std::move(tmp), {start}, {end});
     }
     if (node->modifier == Node::Modifier::Plus) {
-      result.GetVertex(end)->AddEdge(' ', start);
+      result.GetVertex(end).AddEdge(' ', start);
     } else if (node->modifier == Node::Modifier::Star) {
-      result.GetVertex(end)->AddEdge(' ', start);
-      result.GetVertex(start)->AddEdge(' ', end);
+      result.GetVertex(end).AddEdge(' ', start);
+      result.GetVertex(start).AddEdge(' ', end);
     }
   }
   return result;
diff --git a/src/main.cpp b/src/main.cpp
index 701fd02..6cd9217 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -36,7 +36,7 @@ void example2() {
     a[i] = nfa_graph.AddNewVertex();
 
   auto AddEdge = [&nfa_graph, &a](char symbol, int u, int v) {
-    nfa_graph.GetVertex(a[u])->AddEdge(symbol, a[v]);
+    nfa_graph.GetVertex(a[u]).AddEdge(symbol, a[v]);
   };
 
   AddEdge('a', 0, 1);