#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>

int main() {
    std::string string;
    while (std::cin >> string) {
        for (auto end = string.end(); end != string.begin(); --end) {
            auto sub_string = string.substr(0, end - string.begin());
            auto rev_sub_string(sub_string);
            std::reverse(rev_sub_string.begin(), rev_sub_string.end());

            if (sub_string == rev_sub_string) {
                std::cout << sub_string << std::endl;
                break;
            }
        }
    }
    return 0;
}