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:
isivssiivivvi

Ex Output:
ivvi


Ex Input:
iqpqipippqiiiq

Ex Output:
iqpqi


Ex Input:
kmmkkktkmtmkt

Ex Output:

tkmtmkt