#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int64_t N, A;
  cin >> N >> A;
  int64_t sum = 0;
  for (int i = 0; i < N; i++) {
    int64_t a;
    cin >> a;
    sum += a;
  }
  cout << (sum == N * A ? "YES" : "NO") << '\n';
  return 0;
}