diff --git a/alib2algo/src/automaton/transform/AutomataConcatenation.h b/alib2algo/src/automaton/transform/AutomataConcatenation.h
index 9f6cfad00b554eed371d2a216c012389132aae0b..69717cea029b6891663b63117e65d484ed7932fa 100644
--- a/alib2algo/src/automaton/transform/AutomataConcatenation.h
+++ b/alib2algo/src/automaton/transform/AutomataConcatenation.h
@@ -48,47 +48,43 @@ public:
 template < class AutomatonType >
 requires isDFA < AutomatonType > || isNFA < AutomatonType >
 automaton::NFA < typename AutomatonType::SymbolType, ext::pair < typename AutomatonType::StateType, unsigned > > AutomataConcatenation::concatenation ( const AutomatonType & first, const AutomatonType & second ) {
-	unsigned firstDefault = 1;
-	unsigned secondDefault = 2;
+	static const unsigned NONE = 0;
+	static const unsigned FIRST = 1;
+	static const unsigned SECOND = 2;
 
-	using SymbolType = typename AutomatonType::SymbolType;
-	using StateType = typename AutomatonType::StateType;
+	automaton::NFA < typename AutomatonType::SymbolType, ext::pair < typename AutomatonType::StateType, unsigned > > res ( { first.getInitialState ( ), FIRST } );
 
-	automaton::NFA < SymbolType, ext::pair < StateType, unsigned > > res ( ext::make_pair ( first.getInitialState ( ), firstDefault ) );
-
-	for ( const StateType & q : first.getStates ( ) )
-		res.addState ( ext::make_pair ( q, firstDefault ) );
-	for ( const StateType & q : second.getStates ( ) )
-		res.addState ( ext::make_pair ( q, secondDefault ) );
+	for ( const auto & q : first.getStates ( ) )
+		res.addState ( { q, FIRST } );
+	for ( const auto & q : second.getStates ( ) )
+		res.addState ( { q, SECOND } );
 
 	res.addInputSymbols ( first.getInputAlphabet ( ) );
 	res.addInputSymbols ( second.getInputAlphabet ( ) );
 
 	for ( const auto & t : first.getTransitions ( ) ) {
-		res.addTransition ( ext::make_pair ( t.first.first, firstDefault ), t.first.second, ext::make_pair ( t.second, firstDefault ) );
+		res.addTransition ( { t.first.first, FIRST }, t.first.second, { t.second, FIRST } );
 
-		if(first.getFinalStates().count(t.second) > 0)
-			res.addTransition ( ext::make_pair ( t.first.first, firstDefault ), t.first.second, ext::make_pair ( second.getInitialState ( ), secondDefault ) );
+		if ( first.getFinalStates ( ).contains ( t.second ) )
+			res.addTransition ( { t.first.first, FIRST }, t.first.second, { second.getInitialState ( ), SECOND } );
 	}
 
 	for ( const auto& t : second.getTransitions ( ) )
-		res.addTransition ( ext::make_pair ( t.first.first, secondDefault ), t.first.second, ext::make_pair ( t.second, secondDefault ) );
-
-	for ( const StateType & q : second.getFinalStates ( ) )
-		res.addFinalState ( ext::make_pair ( q, secondDefault ) );
+		res.addTransition ( { t.first.first, SECOND }, t.first.second, { t.second, SECOND } );
 
-	if ( first.getFinalStates ( ).count ( first.getInitialState ( ) ) > 0 ) {
-		ext::pair < StateType, unsigned > q01q02 ( label::InitialStateLabel::instance < StateType > ( ), 0 );
+	for ( const auto & q : second.getFinalStates ( ) )
+		res.addFinalState ( { q, SECOND } );
 
+	if ( first.getFinalStates ( ).contains ( first.getInitialState ( ) ) ) {
+		ext::pair < typename AutomatonType::StateType, unsigned > q01q02 ( label::InitialStateLabel::instance < typename AutomatonType::StateType > ( ), NONE );
 		res.addState ( q01q02 );
-
 		res.setInitialState ( q01q02 );
 
 		for ( const auto & t : first.getTransitionsFromState ( first.getInitialState ( ) ) )
-			res.addTransition ( q01q02, t.first.second, ext::make_pair ( t.second, firstDefault ) );
+			res.addTransition ( q01q02, t.first.second, { t.second, FIRST } );
 
 		for ( const auto & t : second.getTransitionsFromState ( second.getInitialState ( ) ) )
-			res.addTransition ( q01q02, t.first.second, ext::make_pair ( t.second, secondDefault ) );
+			res.addTransition ( q01q02, t.first.second, { t.second, SECOND } );
 
 		res.addFinalState ( q01q02 );
 	}