import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        long a = in.nextInt();
        long sum = 0;
        for(int i=0; i<n; i++) {
            sum += in.nextInt();
        }

        if(sum % n == 0 && sum / n == a) System.out.println("YES");
        else System.out.println("NO");

        in.close();
    }
}