instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
AxRSlkQfWHrdlgQG, iXIOrmlkQfWHTy
answer:
lkQfWH


question:
egYXVtCPvWxP, VMOolyVtCPvWjIx
answer:
VtCPvW


question:
cywoEHFwH, gOoEHiy
answer:

oEH