#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < n; ++i)
typedef long long ll;
using namespace std;
const int INF = 1e9;

int main() {
    int n, k;
    cin >> n >> k;

    ll sum = 0;
    rep(i, n) {
        int a;
        cin >> a;
        sum += a;
    }
    if (sum % n == 0 && sum / n == k)
        cout << "YES";
    else
        cout << "NO";
    cout << endl;

    return 0;
}