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:
ssuggsuuugugsg

Ex Output:
uuu


Ex Input:
yyyyyyccwyw

Ex Output:
yyyyyy


Ex Input:
swnnwsnnnnss

Ex Output:

swnnws