using System.Numerics;

public class Program
{
    public static void Main()
    {

        //BigInteger num = BigInteger.Parse(Console.ReadLine() ?? string.Empty);
        int num = int.Parse(Console.ReadLine() ?? string.Empty);
        //string[] moji = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        //string str = Console.ReadLine() ?? string.Empty;

        List<string> list = new List<string>();
        for (int i = 0; i < num; i++)
        {
            string[] moji = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
            list.Add(moji[0]);
            list.Add(moji[1]);
        }
        if(num == 1)
        {
            Console.WriteLine("Yes");
            return;
        }
        string w = "";
        for (int i = 0;i < list.Count;i++)
        {
            int index= list.LastIndexOf(list[i]);
            int d= list.IndexOf(list[i]);
            if (index == i&&d == i)
            {
                continue;
            }
            if(i %  2 == 0)
            {
                w = i.ToString();
            }
            else if(i % 2 != 0&& w != ""&& int.Parse(w) == i-1) 
            {
                Console.WriteLine("No");
                return;
            }
            else if(i%2 !=0&&w!="")
            {
                w = "";
            }
        }
        Console.WriteLine("Yes");

    }

}