func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s, s1;     vector<string> vc;     cin >> s;     for (int i = 0; i < s.size(); i++) {       s1 = s[i];       vc.push_back(s1);       for (int j = i + 1; j < s.size(); j++) {         s1 = s[i];         s1 += s[j];         vc.push_back(s1);         for (int l = j + 1; l < s.size(); l++) {           s1 = s[i];           s1 += s[j];           s1 += s[l];           vc.push_back(s1);           for (int k = l + 1; k < s.size(); k++) {             s1 = s[i];             s1 += s[j];             s1 += s[l];             s1 += s[k];             vc.push_back(s1);             for (int a = k + 1; a < s.size(); a++) {               s1 = s[i];               s1 += s[j];               s1 += s[l];               s1 += s[k];               s1 += s[a];               vc.push_back(s1);               for (int b = a + 1; b < s.size(); b++) {                 s1 = s[i];                 s1 += s[j];                 s1 += s[l];                 s1 += s[k];                 s1 += s[a];                 s1 += s[b];                 vc.push_back(s1);                 for (int c = b + 1; c < s.size(); c++) {                   s1 = s[i];                   s1 += s[j];                   s1 += s[l];                   s1 += s[k];                   s1 += s[a];                   s1 += s[b];                   s1 += s[c];                   vc.push_back(s1);                   for (int d = c + 1; d < s.size(); d++) {                     s1 = s[i];                     s1 += s[j];                     s1 += s[l];                     s1 += s[k];                     s1 += s[a];                     s1 += s[b];                     s1 += s[c];                     s1 += s[d];                     vc.push_back(s1);                     for (int e = d + 1; e < s.size(); e++) {                       s1 = s[i];                       s1 += s[j];                       s1 += s[l];                       s1 += s[k];                       s1 += s[a];                       s1 += s[b];                       s1 += s[c];                       s1 += s[d];                       s1 += s[e];                       vc.push_back(s1);                       for (int f = e + 1; f < s.size(); f++) {                         s1 = s[i];                         s1 += s[j];                         s1 += s[l];                         s1 += s[k];                         s1 += s[a];                         s1 += s[b];                         s1 += s[c];                         s1 += s[d];                         s1 += s[e];                         s1 += s[f];                         vc.push_back(s1);                       }                     }                   }                 }               }             }           }         }       }     }     long long i;     s1 = s[0];     string ans = s1;     for (i = 0; i < vc.size(); i++) {       string p = vc[i];       reverse(p.begin(), p.end());       if (vc[i] == p) {         ans = max(ans, p);       }     }     cout << ans;   }   