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: twwntwnnnttwnw

Output: nnn


Input: Consider Input: vvtvtvvvvt

Output: vvtvtvv


Input: Consider Input: bzzbbtzbztt


Output: tzbzt


