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.

Ex Input:
yvgvvyvyvgg

Ex Output:
vyvyv


Ex Input:
pkckcpckkkckkpk

Ex Output:
kcpck


Ex Input:
xxuxxuxxuuxux

Ex Output:

xxuxxuxx