func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string str;     int n;     cin >> n >> str;     bool flag = true;     int fs = 0, ss = 0;     for (int i = 0; i < n; i++) {       if (str[i] !=  4  && str[i] !=  7 ) {         flag = false;       }     }     for (int i = 0; i < n / 2; i++) {       fs += str[i] -  0 ;     }     for (int i = n / 2; i < n; i++) {       ss += str[i] -  0 ;     }     if (fs != ss) flag = false;     if (flag)       cout <<  YES  << endl;     else       cout <<  NO  << endl;     return 0;   }   