using System;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var ans = Console.ReadLine().Split(' ').ElementAt(1).ToString();
        var avg = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToList().Average();
        Console.WriteLine((avg == double.Parse(ans)) ? "YES" : "NO");
    }
}