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: fvvvvdvddvfdfd
Example Output: vvvv

Example Input: ososoossossoo
Example Output: oossossoo

Example Input: cczzccczzcczczc
Example Output:
cczzccczzcc