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: tcccctctcttctt

Output: tcccct


Input: Consider Input: xrxrrwxrrr

Output: xrx


Input: Consider Input: vkvmvmkmmvm


Output: vkv


