#include "bits/stdc++.h"
using namespace std;

int main() {
	long long int n, a, x, count = 0;
	cin >> n >> a;
	for (int i = 0; i < n; i++) {
		cin >> x;
		count += x;
	}
	if (count == a * n) cout << "YES" << endl;
	else cout << "NO" << endl;
}