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:
mwwummwuwuww

Ex Output:
wuwuw


Ex Input:
zzzmzmrmrmr

Ex Output:
mrmrm


Ex Input:
tttblbttbblbltl

Ex Output:

ttblbtt