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: zaaazavazaa
Example Output: aazavazaa

Example Input: wfhhwwfhhfwh
Example Output: wfhhfw

Example Input: vbivivvbbvi
Example Output:
vbbv