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:
aalzlalzlalz

Ex Output:
alzlalzla


Ex Input:
dcdccddcdkdkdck

Ex Output:
cdkdkdc


Ex Input:
vtttvvttvlt

Ex Output:

ttvvtt