instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
tftBHoDOYxCoTHVf, qhHoDOYxfUU
answer:
HoDOYx


question:
iUtNuU, iKtNWk
answer:
tN


question:
ZhHtTXaUmsQfUMNrnt, KvvebSXaUmsQfBspwM
answer:

XaUmsQf