func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s, tem;     cin >> s;     int m = s.size();     for (int i = 0; i < m; i++) {       if (s[i] !=  a ) tem += s[i];     }     int n = tem.size() / 2;     string sub1 = tem.substr(0, n);     string sub2 = s.substr(m - n, m);     if (sub1 == sub2 && tem.size() % 2 == 0) {       for (int i = 0; i < (m - n); i++) {         cout << s[i];       }     } else {       cout <<  :(  << endl;     }     return 0;   }   