#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int n, a; cin >> n >> a;
    long long sum = 0;
    for (int i = 0; i < n; i++) {
        int x; cin >> x; sum += x;
    }
    cout << (1LL * n * a == sum ? "YES" : "NO") << endl;
    return 0;
}