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:
hpdpdpdpddhdd

Ex Output:
pdpdpdp


Ex Input:
zxzzffzzfx

Ex Output:
zzffzz


Ex Input:
wappppappawpppp

Ex Output:

appppa