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: xmxwwwxxxmwxmxw
Example Output: xwwwx

Example Input: iidititiid
Example Output: ititi

Example Input: ctbtbbbtccctbtt
Example Output:
btccctb

