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:
okoooookykykyok

Ex Output:
koooook


Ex Input:
ssststyysyy

Ex Output:
yysyy


Ex Input:
ffyyyfjfyfjjyyj

Ex Output:

fyyyf