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

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