func_code_string: #include <bits/stdc++.h>   using namespace std;   bool isluck() {     unsigned long long n, s1 = 0, s2 = 0;     string s;     cin >> n >> s;     for (int register i = 0; i < n / 2; i++) {       int x = (s[i] -  0 ) % 10;       if (x != 4 && x != 7) return false;       s1 += x;     }     for (int register i = n / 2; i < n; i++) {       int x = (s[i] -  0 ) % 10;       if (x != 4 && x != 7) return false;       s2 += x;     }     return (s1 == s2);   }   int main() {     isluck() ? cout <<  YES  << endl : cout <<  NO  << endl;     return 0;   }   