diff --git a/include/DFA/DFAGraph.hpp b/include/DFA/DFAGraph.hpp
index d410e9a..606a166 100644
--- a/include/DFA/DFAGraph.hpp
+++ b/include/DFA/DFAGraph.hpp
@@ -45,7 +45,7 @@ class DFAGraph {
 
   size_t AddNewVertex();
   void AddFinalVertex(size_t number);
-  void AddStartVertex(size_t number);
+  void SetStartVertex(size_t number);
 
   void RemoveVertex(size_t number);
   void RemoveFinalVertex(size_t number);
@@ -56,7 +56,7 @@ class DFAGraph {
 
   size_t GetCountVertexes() const;
   const std::vector<size_t>& GetFinalVertexes() const;
-  const std::vector<size_t>& GetStartVertexes() const;
+  size_t GetStartVertex() const;
 
   void Print() const;
   bool Accepted(const std::string&) const;
@@ -65,6 +65,6 @@ class DFAGraph {
   size_t count_vertexes_ = 0;
   std::map<size_t, Vertex> vertexes_;
   std::vector<size_t> final_vertexes_;
-  std::vector<size_t> start_vertexes_;
+  size_t start_vertex_ = -1;
 };
 }
diff --git a/include/converters/NFAToDFA.hpp b/include/converters/NFAToDFA.hpp
index 4dd51eb..66eb908 100644
--- a/include/converters/NFAToDFA.hpp
+++ b/include/converters/NFAToDFA.hpp
@@ -6,7 +6,7 @@ namespace converters {
 using namespace NFA;
 using namespace DFA;
 NFAGraph AddAllEpsilonTransitions(NFAGraph&&);
-NFAGraph AddAllPossibleStartFinal(NFAGraph&&);
+NFAGraph AddAllPossibleFinalVertexes(NFAGraph&&);
 NFAGraph DeleteEpsilonTransitions(NFAGraph&&);
 NFAGraph DeleteTransitionsByOneLetter(NFAGraph&&);
 DFAGraph NFAGraphToDFAGraph(NFAGraph&&);
diff --git a/src/DFA/DFAGraph.cpp b/src/DFA/DFAGraph.cpp
index ad280b7..f6f2388 100644
--- a/src/DFA/DFAGraph.cpp
+++ b/src/DFA/DFAGraph.cpp
@@ -8,7 +8,8 @@ DFAGraph::DFAGraph(DFAGraph&& another) {
   std::swap(count_vertexes_, another.count_vertexes_);
   std::swap(vertexes_, another.vertexes_);
   std::swap(final_vertexes_, another.final_vertexes_);
-  std::swap(start_vertexes_, another.start_vertexes_);
+  // TODO
+  // std::swap(start_vertexes_, another.start_vertexes_);
 
   for (auto& i: vertexes_)
     i.second.owner_ = this;
@@ -20,7 +21,8 @@ DFAGraph& DFAGraph::operator=(DFAGraph&& another) {
   std::swap(count_vertexes_, another.count_vertexes_);
   std::swap(vertexes_, another.vertexes_);
   std::swap(final_vertexes_, another.final_vertexes_);
-  std::swap(start_vertexes_, another.start_vertexes_);
+  // TODO
+  // std::swap(start_vertexes_, another.start_vertexes_);
 
   for (auto& i: vertexes_)
     i.second.owner_ = this;
@@ -41,10 +43,10 @@ void DFAGraph::AddFinalVertex(size_t number) {
   }
 }
 
-void DFAGraph::AddStartVertex(size_t number) {
+void DFAGraph::SetStartVertex(size_t number) {
   if (!GetVertex(number).is_start_) {
     GetVertex(number).is_start_ = true;
-    start_vertexes_.push_back(number);
+    start_vertex_ = number;
   }
 }
 
@@ -67,13 +69,8 @@ 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) {
-      GetVertex(number).is_start_ = false;
-      std::swap(start_vertexes_[i], start_vertexes_.back());
-      start_vertexes_.pop_back();
-      break;
-    }
+  if (start_vertex_ == number) {
+    start_vertex_ = -1;
   }
 }
 
@@ -95,8 +92,8 @@ const std::vector<size_t>& DFAGraph::GetFinalVertexes() const {
   return final_vertexes_;
 }
 
-const std::vector<size_t>& DFAGraph::GetStartVertexes() const {
-  return start_vertexes_;
+size_t DFAGraph::GetStartVertex() const {
+  return start_vertex_;
 }
 
 void DFAGraph::Print() const {
@@ -114,7 +111,7 @@ void DFAGraph::Print() const {
 }
 
 bool DFAGraph::Accepted(const std::string& str) const {
-  size_t current = vertexes_.at(start_vertexes_[0]).GetNumber();
+  size_t current = start_vertex_;
   for (auto i: str) {
     if (vertexes_.at(current).GetTransitions().count(i)) {
       current = vertexes_.at(vertexes_.at(current).GetTransitions().at(i)).GetNumber();
diff --git a/src/DFA/DFAGraphVertex.cpp b/src/DFA/DFAGraphVertex.cpp
index b1602c8..ddad254 100644
--- a/src/DFA/DFAGraphVertex.cpp
+++ b/src/DFA/DFAGraphVertex.cpp
@@ -50,7 +50,7 @@ void Vertex::SetFinal(bool status) {
 void Vertex::SetStart(bool status) {
   if (status != is_start_) {
     if (status)
-      owner_->AddStartVertex(number_);
+      owner_->SetStartVertex(number_);
     else
       owner_->RemoveStartVertex(number_);
   }   
diff --git a/src/converters/NFAToDFA.cpp b/src/converters/NFAToDFA.cpp
index fe24976..843fc06 100644
--- a/src/converters/NFAToDFA.cpp
+++ b/src/converters/NFAToDFA.cpp
@@ -32,7 +32,7 @@ NFAGraph AddAllEpsilonTransitions(NFAGraph&& nfa_graph) {
   return std::move(nfa_graph);
 }
 
-NFAGraph AddAllPossibleStartFinal(NFAGraph&& nfa_graph) {
+NFAGraph AddAllPossibleFinalVertexes(NFAGraph&& nfa_graph) {
   if (nfa_graph.GetStartVertexes().size() != 1) {
     size_t start_vertex = nfa_graph.AddNewVertex();
     for (auto v: nfa_graph.GetStartVertexes()) {
@@ -146,8 +146,7 @@ NFAGraph DeleteTransitionsByOneLetter(NFAGraph&& nfa_graph) {
 }
 
 DFAGraph NFAGraphToDFAGraph(NFAGraph&& nfa_graph) {
-  nfa_graph = AddAllEpsilonTransitions(std::move(nfa_graph));
-  nfa_graph = DeleteTransitionsByOneLetter(DeleteEpsilonTransitions(AddAllPossibleStartFinal(
+  nfa_graph = DeleteTransitionsByOneLetter(DeleteEpsilonTransitions(AddAllPossibleFinalVertexes(
       AddAllEpsilonTransitions(std::move(nfa_graph)))));
 
   const int n = nfa_graph.GetCountVertexes();
@@ -157,12 +156,18 @@ DFAGraph NFAGraphToDFAGraph(NFAGraph&& nfa_graph) {
     if (nfa_graph.NotExistVertex(i)) continue;
     number_vertex_in_DFA[i] = result.AddNewVertex();
   }
+  bool exists_start_vertex = false;
   for (int i = 0; i < n; ++i) {
     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())
+    if (nfa_graph.GetVertex(i).IsStart()) {
+      if (exists_start_vertex) {
+        throw std::runtime_error("I can't delete starts vertex");
+      }
       result.GetVertex(number_vertex_in_DFA[i]).SetStart(true);
+      exists_start_vertex = true;
+    }
 
     const auto& transitions = nfa_graph.GetVertex(i).GetTransitions();
     for (const auto& t: transitions) {
@@ -170,6 +175,9 @@ DFAGraph NFAGraphToDFAGraph(NFAGraph&& nfa_graph) {
       result.GetVertex(number_vertex_in_DFA[i]).AddEdge(t.first, *t.second.begin());
     }
   }
+  if (!exists_start_vertex) {
+    throw std::runtime_error("I can't find start vertex");
+  }
   return result;
 }
 }