func_code_string: #include <bits/stdc++.h>   using namespace std;   using int64 = long long;   int main() {     string s;     cin >> s;     int v[26] = {};     for (auto &c : s) v[c -  a ]++;     deque<int> odd;     for (int i = 0; i < 26; i++) {       if (v[i] % 2 == 1) odd.emplace_back(i);     }     while (odd.size() >= 2) {       int p = odd.front();       int q = odd.back();       odd.pop_front();       odd.pop_back();       v[p]++;       v[q]--;     }     string pre;     for (int i = 0; i < 26; i++) {       int t = v[i] / 2;       while (t--) pre += (char)(i +  a );     }     cout << pre;     if (odd.size()) cout << (char)( a  + odd[0]);     reverse(begin(pre), end(pre));     cout << pre << endl;   }   