In this task you will be given a string and you should find the longest substring that is a palindrome. A palindrome is a string that is the same backwards as it is forwards. If the shortest possible palindrome is length 1 you should return the first character.

Input: Consider Input: ttytrtrtytr

Output: tytrtrtyt


Input: Consider Input: oskksksokkkkoso

Output: sokkkkos


Input: Consider Input: srssrsssssss


Output: sssssss