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:
yyyiyyyiyiy

Ex Output:
yyyiyyy


Ex Input:
rrqqllqrlllr

Ex Output:
rlllr


Ex Input:
kmmkaakkmkaa

Ex Output:

kmmk


