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

int main(){
    int N;
    cin >> N;
    vector<string> S(N), T(N);
    for (int i = 0; i < N; i++) cin >> S[i] >> T[i];

    for (int i = 0; i < N; i++){
        bool s = true, t = true;
        for (int j = 0; j < N; j++) if (i != j){
            if (S[i] == S[j] || S[i] == T[j]) s = false;
            if (T[i] == S[j] || T[i] == T[j]) t = false;
        }
        if (!s && !t){
            cout << "No" << endl;
            return 0;
        }
    }

    cout << "Yes" << endl;
}