import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import static java.lang.System.in;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String[] inputs = reader.readLine().split(" ");
        int n = Integer.parseInt(inputs[0]);
        int a = Integer.parseInt(inputs[1]);
        inputs = reader.readLine().split(" ");
        long sum = 0;
        for (int i = 0; i < n; i++) {
            sum += Long.parseLong(inputs[i]);
        }
        if((a*n) == sum) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
}