instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
PivhPfah, XSghPfOi
answer:
hPf


question:
HSsyZzZLZAAq, MFEZzZLJC
answer:
ZzZL


question:
jPFhsKnJHDKfrIoUoljXvjHg, qUDKfrIoUoljzEflAgVeP
answer:

DKfrIoUolj