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: uuuuuuuuuuu
Example Output: uuuuuuuuuuu

Example Input: kuoukooouokk
Example Output: kuouk

Example Input: nvnnvpvpnvvpp
Example Output:
vnnv

