func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = int(1e5 + 3);   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     string s;     cin >> s;     int size = s.length();     int count4 = 0;     int count7 = 0;     for (int i = 0; i < size; i++) {       if (s[i] ==  7 ) count7++;       if (s[i] ==  4 ) count4++;     }     if (count4 == 0 && count7 == 0)       cout << -1 <<   n ;     else if (count4 >= count7)       cout << 4 <<   n ;     else       cout << 7 <<   n ;   }   