/* -*- coding: utf-8 -*-
 *
 * 3196.cc:  No.3196 Unique Nickname - yukicoder
 */

#include<cstdio>
#include<string>
#include<map>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 100;

/* typedef */

using msi = map<string,int>;

/* global variables */

string ss[MAX_N], ts[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  msi scs;
  for (int i = 0; i < n; i++) {
    char s[32], t[32];
    scanf("%s%s", s, t);
    string si(s), ti(t);
    ss[i] = si, ts[i] = ti;
    scs[si]++, scs[ti]++;
  }

  for (int i = 0; i < n; i++)
    if (scs[ss[i]] > 1 && scs[ts[i]] > 1) {
      puts("No");
      return 0;
    }

  puts("Yes");
  return 0;
}