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

int main() {
    long long N, K;
    cin >> N >> K;
    long long sum = 0;
    for(int i = 0; i < N; ++i) {
        long long x;
        cin >> x;
        sum += x;
    }
    if(sum == N*K) cout << "YES" << endl;
    else cout << "NO" << endl;
}