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: ddnndgnddngdd

Output: dgnddngd


Input: Consider Input: oxxoxoxxxxx

Output: xxoxoxx


Input: Consider Input: vkekekkvek


Output: kekek