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:
tbpptbtbttpbp
answer:
tbtbt


question:
tnnntntnnn
answer:
nnntntnnn


question:
ldjjllldddlljd
answer:

lldddll