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:
zvzzzdzzvdz
answer:
zzdzz


question:
qwqwaaqwqwaaw
answer:
waaw


question:
nnkknmmmkk
answer:

nkkn