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.

Ex Input:
iiddididijjiijd

Ex Output:
didid


Ex Input:
nynygnggynyggg

Ex Output:
ggynygg


Ex Input:
vkvvdvvddvkkd

Ex Output:

vvdvv