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

class Program
{
    static void Main(string[] args)
    {
        int[] ary = Console.ReadLine().Split().Select(v => int.Parse(v)).ToArray();
        int[] x = Console.ReadLine().Split().Select(v => int.Parse(v)).ToArray();

        string ans = "NO";

        if (ary[1] == x.Average())
        {
            ans = "YES";
        }

        Console.WriteLine(ans);
        Console.ReadLine();
    }
}