#pragma GCC optimize ( "O3" )
#pragma GCC optimize ( "unroll-loops" )
#pragma GCC target ( "sse4.2,fma,avx2,popcnt,lzcnt,bmi2" )
#include <bits/stdc++.h>
using namespace std;

int main()
{
  ios_base::sync_with_stdio( false ); cin.tie( nullptr );
  int N; cin >> N;
  vector<int> S( N ) , T( N );
  for( int i = 0 ; i < N ; i++ ){
    cin >> S[i] >> T[i];
  }
  int s;
  int t;
  bool b = false;
  for( int i = 1 ; i < N ; i++ ){
    s = S[i];
    t = T[i];
    for( int j = 0 ; j < i ; j++ ){
      b |= s == S[j] && t != T[j];
    }
  }
  cout << ( b ? "No" : "Yes" ) << "\n";
}