#include <bits/stdc++.h>

using namespace std;

int main() {
    int N;
    cin >> N;
    vector<pair<string, string>> V;
    map<string, int> cnt;
    for (int i = 0; i < N; i++) {
        string S, T;
        cin >> S >> T;
        V.emplace_back(S, T);
        cnt[S]++, cnt[T]++;
    }
    bool ok = true;
    for (int i = 0; i < N; i++) {
        ok &= cnt[V[i].first] == 1 || cnt[V[i].second] == 1;
    }
    cout << (ok ? "Yes": "No") << endl;
    return 0;
}