#include <iostream>
#include <vector>
#include <algorithm>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)

using namespace std;

typedef long long int lli;

int main() {
    lli N, A;
    cin >> N >> A;
    lli sum = 0;
    REP (i, 0, N) {
        int tmp;
        cin >> tmp;
        sum += tmp;
    }
    cout << (N * A == sum ? "YES" : "NO") << endl;
    return 0;
}