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: hhwwhwiwwhi
Example Output: hwwh

Example Input: vevrervevrrvev
Example Output: vevrervev

Example Input: iiiivvkviikvki
Example Output:
ikvki