#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define o(a) cout << a << endl
#define int long long
using namespace std;
typedef pair<int, int> P;

signed main(){
    int n, a;
    cin >> n >> a;
    int sum = 0;
    vector<int> d(n);
    rep(i, 0, n){
        cin >> d[i];
        sum += d[i];
    }
    if(sum == n * a) cout << "YES" << endl;
    else cout << "NO" << endl;
}