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: lljljljjjjjljj
Example Output: jljjjjjlj

Example Input: qqqqqqgqggqqqgg
Example Output: ggqqqgg

Example Input: vvkvzvzkkvkkv
Example Output:
kkvkk

