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.

Input: Consider Input: simiisismmmsiss

Output: sismmmsis


Input: Consider Input: ggtrtgrrtrgr

Output: gtrtg


Input: Consider Input: acaackccac


Output: caac


