instruction:
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.
question:
nnngggununngnn
answer:
nngnn


question:
gvvvgvyvyy
answer:
gvvvg


question:
yyvjjyvvyvyvy
answer:

vyvyv