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:
fvvvvdvddvfdfd

Ex Output:
vvvv


Ex Input:
kuoukooouokk

Ex Output:
kuouk


Ex Input:
ddtdttdttdddttt

Ex Output:

dttdttd