instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
CiTNsbepy, DFNsbeZl
answer:
Nsbe


question:
WlqGjLNrxXeUrKCZel, pDSsmNrxXeUrKCslBXBbRu
answer:
NrxXeUrKC


question:
AxRSlkQfWHrdlgQG, iXIOrmlkQfWHTy
answer:

lkQfWH


