instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
lypuwWy, jRpuwcE
answer:
puw


question:
AxRSlkQfWHrdlgQG, iXIOrmlkQfWHTy
answer:
lkQfWH


question:
zjxdQdsTDMtDfmwZ, SRaZNKsTDMtDVltIG
answer:

sTDMtD