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:
puppppppppup

Ex Output:
puppppppppup


Ex Input:
nnqnqqnnnn

Ex Output:
nqqn


Ex Input:
kassaksaskssksk

Ex Output:

kassak