using System;
using System.Collections.Generic;
using System.Linq;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] x = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int[] a = Console.ReadLine().Split().Select(int.Parse).ToArray();
            double ave = a.Average();
            Console.WriteLine(a.Average() == x[1] ? "YES" : "NO");
        }
    }
}