#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main(void) {
  ll n, a;
  cin >> n >> a;
  
  ll sum = 0;
  for (int i = 0; i < n; i++) {
    ll x;
    cin >> x;
    sum += x;
  }

  cout << (sum == n * a ? "YES": "NO") << endl;

  return 0;
}