#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, n) for (int i = a; i < (int)(n); i++)
using ll = long long;

int main()
{
    int n;
    cin >> n;
    map<string, int> mp;
    vector<string> f(n), l(n);
    rep(i, 0, n)
    {
        cin >> f[i] >> l[i];
        mp[f[i]]++;
        mp[l[i]]++;
    }
    bool ok = true;
    rep(i, 0, n)
    {
        if (mp[f[i]] > 1 && mp[l[i]] > 1)
        {
            ok = false;
            break;
        }
    }
    cout << (ok ? "Yes\n" : "No\n");
}