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:
yynnhyynnyn

Ex Output:
ynny


Ex Input:
ukuukmmkuu

Ex Output:
uukmmkuu


Ex Input:
vpvvbbvvppbpvp

Ex Output:

pvvbbvvp