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

using ll = long long;
#define rep(i, a, n) for(int i = a; i < n; i++)

int main() {
	int N;
	cin >> N;
	vector<string> s(N), t(N);
	rep(i, 0, N) cin >> s[i] >> t[i];
	rep(i, 0, N) {
		int f = 0, g = 0;
		rep(j, 0, N) {
			if(j == i) continue;
			if(s[i] == s[j] || s[i] == t[j]) f = 1;
		}
		rep(j, 0, N) {
			if(j == i) continue;
			if(t[i] == s[j] || t[i] == t[j]) g = 1;
		}
		if(f && g) {
			cout << "No" << endl;
			return 0;
		}
	}
	cout << "Yes" << endl;
}