#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;
using ll = long long;

int main(){
  int n; cin >> n;
  vector<string> s(n), t(n);
  map<string, int> cnt;
  for(int i=0; i<n; i++) cin >> s[i] >> t[i], cnt[s[i]]++, cnt[t[i]]++;
  for(int i=0; i<n; i++){
    if(cnt[s[i]]!=1&&cnt[t[i]]!=1){
      cout << "No" << endl; return 0;
    }
  }
  cout << "Yes" << endl;
  return 0;
}