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

int main()
{
    long long n, a; cin >> n >> a;
    
    long long s = 0;
    for (int i = 0; i < n; i++) {
        int b; cin >> b;
        s += b;
    }

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

    return 0;
}