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:
qvvqvpvvqvvvq

Ex Output:
vvqvv


Ex Input:
hhhuumhhhumumu

Ex Output:
umumu


Ex Input:
uuguuuguuuuu

Ex Output:

uuguuuguu