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: ljjljjllllj
Example Output: ljjljjl

Example Input: bbbabaxxxa
Example Output: axxxa

Example Input: bpbcpbcbcppb
Example Output:
bpb