func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long i, j, k, n, m, z, c;     string s;     cin >> s;     c = 0, z = 0;     for (i = 0; i < s.size(); i++) {       if (s[i] ==  4 )         c++;       else if (s[i] ==  7 )         z++;     }     if (c == z && z == 0)       cout << -1 << endl;     else if (c >= z)       cout << 4 << endl;     else       cout << 7 << endl;   }   