using System;

public class Program {
	public void Solve() {
		string[] s = Console.ReadLine().Split(' ');
		string[] x = Console.ReadLine().Split(' ');
		int a = int.Parse(s[1]);
		long sum = 0;
		for (int i = 0; i < x.Length; i++) {
			sum += int.Parse(x[i]);
		}
		if (a == (double)sum / x.Length) {
			Console.WriteLine("YES");
		} else {
			Console.WriteLine("NO");
		}
	}
	
	public static void Main(string[] args) {
		Program program = new Program();
		program.Solve();
	}
}