#include <iostream>
using namespace std;

int main(void){
    int n,a,i;
    long long num;
    int  *x;
    long long res;
    
    cin >> n >> a;
    x = new int[n];
    for(i=0;i<n;i++){
        cin >> x[i];
        num += x[i];
    }
    res = num/n;
    if(res != a){
        cout << "NO\n";
    }else{
        cout << "YES\n";
    }
    return (0);
}