#include <bits/stdc++.h>
using namespace std;

#define TYPE_OF( VAR ) remove_const<remove_reference<decltype( VAR )>::type >::type
#define UNTIE ios_base::sync_with_stdio( false ); cin.tie( nullptr ) 
#define CEXPR( LL , BOUND , VALUE ) constexpr const LL BOUND = VALUE 
#define CIN( LL , A ) LL A; cin >> A 
#define ASSERT( A , MIN , MAX ) assert( ( MIN ) <= A && A <= ( MAX ) ) 
#define CIN_ASSERT( A , MIN , MAX ) CIN( TYPE_OF( MAX ) , A ); ASSERT( A , MIN , MAX ) 
#define FOR( VAR , INITIAL , FINAL_PLUS_ONE ) for( TYPE_OF( FINAL_PLUS_ONE ) VAR = INITIAL ; VAR < FINAL_PLUS_ONE ; VAR ++ ) 
#define REPEAT( HOW_MANY_TIMES ) FOR( VARIABLE_FOR_REPEAT , 0 , HOW_MANY_TIMES ) 
#define QUIT return 0 
#define COUT( ANSWER ) cout << ( ANSWER ) << "\n"; 
#define RETURN( ANSWER ) COUT( ANSWER ); QUIT 

int main()
{
  UNTIE;
  CEXPR( int , bound_N , 4 );
  CIN_ASSERT( N , 1 , bound_N );
  CEXPR( int , bound_M , ( bound_N * ( bound_N - 1 ) ) / 2 );
  CIN_ASSERT( M , 0 , bound_M );
  int ij[bound_M*2][2];
  FOR( m , 0 , M ){
    CIN( int , im );
    CIN( int , jm );
    assert( 0 <= im && im < jm && jm < N );
    FOR( k , 0 , m ){
      assert( ij[k][0] != im || ij[k][1] != jm );
    }
    ij[m][0] = ij[m+M][1] = im;
    ij[m][1] = ij[m+M][0] = jm;
  }
  set<int> vertex_exception{};
  REPEAT( 3 ){
    CIN_ASSERT( v , 0 , N - 1 );
    vertex_exception.insert( v );
  }
  int M2 = M * 2;
  FOR( m0 , 0 , M2 ){
    FOR( m1 , 0 , M2 ){
      FOR( m2 , 0 , M2 ){
	if( tuple<int,int,int>( ij[m0][1] , ij[m1][1] , ij[m2][1] ) == tuple<int,int,int>( ij[m1][0] , ij[m2][0] , ij[m0][0] ) ){
	  set<int> edge{ m0 % M , m1 % M , m2 % M };
	  set<int> vertex{ ij[m0][0] , ij[m1][0] , ij[m2][0] };
	  if( vertex.size() == 3 && edge.size() == 3 && vertex != vertex_exception ){
	    RETURN( "Yes" );
	  }
	  continue;
	}
	FOR( m3 , 0 , M2 ){
	  if( tuple<int,int,int,int>( ij[m0][1] , ij[m1][1] , ij[m2][1] , ij[m3][1] ) == tuple<int,int,int,int>( ij[m1][0] , ij[m2][0] , ij[m3][0] , ij[m0][0] ) ){
	    set<int> edge{ m0 % M , m1 % M , m2 % M , m3 % M };
	    set<int> vertex{ ij[m0][0] , ij[m1][0] , ij[m2][0] , ij[m3][0] };
	    if( vertex.size() == 4 && edge.size() == 4 ){
	      RETURN( "Yes" );
	    }
	    continue;
	  }
	}
      }
    }
  }
  RETURN( "No" );
}