func_code_string: #include <bits/stdc++.h>   using namespace std;   long long int lar(long long int a, long long int b) {     return ((a >= b) ? a : b);   }   long long int les(long long int a, long long int b) {     return ((a <= b) ? a : b);   }   int main() {     string s;     cin >> s;     vector<string> v;     long long int a = 0, b = 0;     for (long long int i = 0; i < s.size(); i++) {       if (s[i] ==  4 )         a++;       else if (s[i] ==  7 )         b++;     }     if (a == 0 && b == 0) {       cout << -1 << endl;       return 0;     }     if (a >= b)       cout <<  4  << endl;     else       cout <<  7  << endl;     return 0;   }   