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

int main()
{
  int N; cin >> N;
  constexpr const int bound_s = 100000;
  vector<int> F( bound_s + 1 , -1 );
  for( int i = 0 ; i < N ; i++ ){
    int s; cin >> s;
    int t; cin >> t;
    if( F[s] == -1 || F[s] == t ){
      F[s] = t;
    } else {
      cout << "No\n";
      return 0;
    }
  }
  cout << "Yes\n";
  return 0;
}