#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll mod = 1e9 + 7;
const int N = 200005;
const int INF = 0x3f3f3f3f;
string s[N], t[N];
int main() {
    int n;
    cin >> n;
    map<string, int> mp;
    for (int i = 0; i < n; i++) {
        cin >> s[i] >> t[i];
        mp[s[i]]++;
        mp[t[i]]++;
    }
    for (int i = 0; i < n; i++) {
        if (mp[s[i]] > 1 && mp[t[i]] > 1) {
            cout << "No\n";
            return 0;
        }
    }
    cout << "Yes\n";
    return 0;
}