func_code_string: #include <bits/stdc++.h>   using namespace std;   int i;   int main() {     string s;     cin >> s;     int k;     i = 0;     while (s[i] ==  0 ) {       i++;     }     int f = 0, v = 0;     bool b = false;     while (i != s.size()) {       if (s[i] ==  4 )         f++;       else if (s[i] ==  7 )         v++;       i++;     }     if (b)       cout << -1;     else {       if (f != 0 && f == v)         cout << 4;       else if (f > v)         cout << 4;       else if (v > f)         cout << 7;       else         cout << -1;     }   }   