func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s;     cin >> s;     int l = s.length();     int fc = 0;     int sc = 0;     for (int i = 0; i < l; i++) {       if (s[i] ==  4 ) fc++;       if (s[i] ==  7 ) sc++;     }     if (!fc && !sc)       cout <<  -1  << endl;     else if (sc > fc)       cout <<  7  << endl;     else       cout <<  4  << endl;     return 0;   }   