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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<pair<string, string>> a(n);
    map<string, int> mp;
    for(auto &&[x, y] : a){
        cin >> x >> y;
        mp[x]++;
        mp[y]++;
    }
    for(auto &&[x, y] : a){
        if(!(mp[x] == 1 || mp[y] == 1 || (x == y && mp[x] == 2))){
            cout << "No\n";
            return 0;
        }
    }
    cout << "Yes\n";
}