import java.util.*;

class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		
		long n = sc.nextLong(); long favg = sc.nextLong();
		Long sum = 0L;
		for (int i=0; i<n; i++) {
			sum += sc.nextInt() * n;
		}
		
		System.out.println(sum/n==favg*n?"YES":"NO");
		
	}
}