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: yyvyvvyynnyv

Output: yvvy


Input: Consider Input: hhhrhhhhrhr

Output: hrhhhhrh


Input: Consider Input: vfnvfnvvvvvnvf


Output: nvvvvvn