//https://atcoder.jp/contests/adt_all_20250109_2/submissions/61497078より.

#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (ll)(n); i++)
#define all(a) (a).begin(), (a).end()
using ll = long long;
const int INF32 = 2e9;
const ll INF64 = 4e18;

int main() {
    int N;
    cin >> N;
    vector<pair<string, string>> st(N);
    map<string, int> list;
    rep(i, N) {
        string si, ti;
        cin >> si >> ti;
        st[i] = make_pair(si, ti);
        if (list.count(si)) {
            list[si]++;
        } else
            list[si] = 0;
        if (si == ti)
            continue;
        if (list.count(ti)) {
            list[ti]++;
        } else
            list[ti] = 0;
    }
    bool ans = true;
    rep(i, N) {
        if (list[st[i].first] > 0 && list[st[i].second])
            ans = false;
    }
    if (ans)
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
    return 0;
}