#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
using ll = long long;

int main() {
    int n;
    cin >> n;
    vector<vector<string>> temp(n, vector<string>());
    rep(i, n) {
        string s, t;
        cin >> s >> t;
        temp[i].push_back(s);
        temp[i].push_back(t);
    }
    rep(i, n) {
        bool ok_s = true;
        bool ok_t = true;
        rep(j, n) {
            if (i == j) continue;
            if (temp[i][0] == temp[j][0] || temp[i][0] == temp[j][1])
                ok_s = false;
            if (temp[i][1] == temp[j][0] || temp[i][1] == temp[j][1])
                ok_t = false;
        }
        if (!ok_s && !ok_t) {
            cout << "No" << endl;
            return 0;
        }
    }
    cout << "Yes" << endl;
    return 0;
}