#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 QUIT return 0 
#define COUT( ANSWER ) cout << ( ANSWER ) << "\n";
#define RETURN( ANSWER ) COUT( ANSWER ); QUIT

#define MAIN main

int MAIN()
{
  UNTIE;
  CEXPR( int , bound , 100000 );
  CIN_ASSERT( N , 0 , bound );
  vector<int> S( N ) , T( N );
  FOR( i , 0 , N ){
    CIN_ASSERT( s , 0 , bound );
    CIN_ASSERT( t , 0 , bound );
    S[i] = s;
    T[i] = t;
  }
  int s;
  int t;
  FOR( i , 1 , N ){
    s = S[i];
    t = T[i];
    FOR( j , 0 , i ){
      if( s == S[j] && t != T[j] ){
	RETURN( "No" );
      }
    }
  }
  RETURN( "Yes" );
}