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: aamaaahaham
Example Output: aamaa

Example Input: hpdpdpdpddhdd
Example Output: pdpdpdp

Example Input: yyayyayyayyayk
Example Output:
yayyayyayyay