func_code_string: #include <bits/stdc++.h>   double pi = 3.1415926535897931159979635;   using namespace std;   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     long long cf = 0, cs = 0, c47 = 0, c74 = 0;     string a;     cin >> a;     long long s = a.size();     for (int i = 0; i < s; i++) {       if (a[i] ==  4 ) {         cf++;         if (a[i - 1] ==  7  && i > 0) c74++;       } else if (a[i] ==  7 ) {         cs++;         if (a[i - 1] ==  4  && i > 0) c47++;       }     }     if (cf == 0 && cs == 0)       cout <<  -1 n ;     else       s = max(c47, max(c74, max(cf, cs)));     if (s == cf)       cout <<  4 n ;     else if (s == cs)       cout <<  7 n ;     else if (s == c47)       cout <<  47 n ;     else if (s == c74)       cout <<  74 n ;     return 0;   }   