#include <iostream>
#define REP(i, n) for (int i = 0; i < n; i++)
typedef long long ll;
using namespace std;

int main(void) {
    ll n, a, sum;
    cin >> n >> a;
    sum = 0;
    REP(i, n) {
        ll x;
        cin >> x;
        sum += x;
    }
    if (sum == n * a) cout << "YES" << endl;
    else cout << "NO" << endl;
    return 0;
}