#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
#define DEBUG

int main()
{
    ll n, k, s, d;
    cin >> n >> k;
    s = 0;
    rep(i, n){
        cin >> d;
        s += d;
    }
    
    cout << ( ( s == n * k ) ? "YES" : "NO" );
    
    
    return 0;
}