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.

Example Input: tttllllltl
Example Output: tlllllt

Example Input: kkoeekoookeo
Example Output: ekoooke

Example Input: kbbnbbnkbnkbkb
Example Output:
bbnbb