using c=System.Console;
using System.Linq;
public class Yuki{
	public static void Main(){
		var x = c.ReadLine().Split(' ').Select(n=>int.Parse(n)).ToList();
		var y = c.ReadLine().Split(' ').Select(n=>int.Parse(n)).ToList();
		var a=(x[1]==y.Average())?"YES":"NO";
		c.WriteLine(a);
	}
}