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

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N;
    cin >> N;
    vector<pair<string, string>> V(N);
    map<string, int> mp;
    for (auto &[a, b] : V)
    {
        cin >> a >> b;
        mp[a]++;
        mp[b]++;
    }
    for (auto [a, b] : V)
    {
        if (mp[a] != 1 && mp[b] != 1)
        {
            cout << "No" << endl;
            return 0;
        }
    }
    cout << "Yes" << endl;
    return 0;
}