using System.Collections.Generic;
using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        getAns(n);
    }
    static void getAns(int n)
    {
        var d = new Dictionary<string, int>();
        var input = new (string s, string t)[n];
        for (int i = 0; i < n; i++)
        {
            string[] line = Console.ReadLine().Trim().Split(' ');
            var s = line[0];
            var t = line[1];
            if (d.ContainsKey(s)) d[s]++;
            else d[s] = 1;
            if (d.ContainsKey(t)) d[t]++;
            else d[t] = 1;
            input[i] = (s, t);
        }
        for (int i = 0; i < n; i++)
        {
            if (d[input[i].s] > 1 && d[input[i].t] > 1) { Console.WriteLine("No"); return; }
        }
        Console.WriteLine("Yes");
    }
}