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:
dyddyybbbdy

Ex Output:
yddy


Ex Input:
luloouolouu

Ex Output:
uolou


Ex Input:
ggpnnpgpgpgpg

Ex Output:

pgpgpgp