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

int main() {
  int64_t n, a, s = 0;
  cin >> n >> a;
  for (int i = 0; i < n; i++) {
    int64_t x;
    cin >> x;
    s += x;
  }
  cout << ((s == n * a) ? "YES" : "NO") << endl;
  return 0;
}