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.

Example Input: tcccctctcttctt
Example Output: tcccct

Example Input: iiikrriikrrki
Example Output: ikrrki

Example Input: rnmnrmmnmnr
Example Output:
rnmnr