#include <bits/stdc++.h>   using namespace std;   int main() {     int n, m = 0;     cin >> n;     int last;     for (int(i) = 0; (i) < (n); ++(i)) {       cin >> last;       m += last;     }     cout << ((n - m == 1 && n > 1) || (n == 1 && m == 1) ?  YES n  :  NO n );   }   