import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Scanner;

public class Main {
	
	public static long MOD = 1000000007;
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int n = sc.nextInt();
		final long a = sc.nextLong();
		
		long sum = 0;
		for(int i = 0; i < n; i++){
			sum += sc.nextLong();
		}
		
		System.out.println(sum == n * a ? "YES" : "NO");
	}
}