using System;
using System.Linq;

public class Program
{
	public static void Main()
	{
		var na = Console.ReadLine().Split().Select(int.Parse);
		int n = na.First(), a = na.Last();
		var x = Console.ReadLine().Split().Select(int.Parse);
		Console.WriteLine(x.Average() == a ? "YES" : "NO");
	}
}