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: pppuupppppuu

Output: uupppppuu


Input: Consider Input: slusssllluls

Output: sss


Input: Consider Input: zzaqzqzqaz


Output: zaqzqzqaz