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: tttttfttfttff
Example Output: ttfttftt

Example Input: dcdccddcdkdkdck
Example Output: cdkdkdc

Example Input: yyhyhhhyrhhhrr
Example Output:
yhhhy

