instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
UvYbfKFybXofcwLRrLRiK, BgMZKFybXofcVe
answer:
KFybXofc


question:
BVipiZoGXaWdjmDsxWP, yxppsiYkiZoGXaWdjoDRuKW
answer:
iZoGXaWdj


question:
AtdZKYeorJMa, aONUDZKYeohZ
answer:

ZKYeo