using System;
using System.Linq;

namespace _0325
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] s = new string[6];
            int[] a = new int[6];
            int[] b = new int[6];
            for (int i = 0; i < 6; i++)
            {
                int[] x = Console.ReadLine().Split().Select(int.Parse).ToArray();
                Array.Sort(x);
                s[i] = x[0] + " " + x[1];
                a[i] = x[0];
                b[i] = x[1];
            }
            Array.Sort(s);
            Array.Sort(a);
            Array.Sort(b);
            bool ok = true;
            for (int i = 0; i < 3 && ok; i++)
            {
                if (s[i * 2] != s[i * 2 + 1])
                {
                    ok = false;
                }
            }
            if (a[2] != b[0] || a[3] != b[1])
            {
                ok = false;
            }
            Console.WriteLine(ok ? "yes" : "no");
            //Console.ReadLine();
        }
    }
}