#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  vector<pair<string, string>> v(n);
  for (auto& [a, b] : v) cin >> a >> b;
  map<string, int> st;
  for (auto& [a, b] : v) st[a]++, st[b]++;
  bool ok = true;
  for (auto& [a, b] : v) ok &= st[a] == 1 || st[b] == 1;
  cout << (ok ? "Yes" : "No") << '\n';
  return 0;
}