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: ffyfyfyynf
Example Output: fyfyf

Example Input: dvmdmdvmdmm
Example Output: mdm

Example Input: bipppbpbbbb
Example Output:
bbbb