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

int main() {
  long long n, a, sum = 0;
  cin >> n >> a;
  for (int i = 0, x; i < n && cin >> x; i++) sum += x;

  cout << ((sum % n) ? "NO" : (sum / n == a) ? "YES" : "NO") << "\n";
}