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:
tftBHoDOYxCoTHVf, qhHoDOYxfUU
answer:
HoDOYx


question:
CzJyPYFG, ONJyPWY
answer:

JyP