func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long b, c, d, e, f, g, h, i, j = 0, k = 2, l, o = 0, m = 0, n = 0, q = 1,                                       r = 1, s, t, u, v, x = 1, y = 1,                                       z = 1111111;     string a;     cin >> a;     b = a.size();     for (i = 0; i < b; i++) {       if (a[i] ==  4 ) n++;       if (a[i] ==  7 ) m++;     }     if (n == 0 && m == 0) {       cout << -1;       return 0;     }     if (m > n)       cout << 7;     else       cout << 4;   }   