instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
vMsEJRoLkWcmkuwNRz, ZmoLkWcmVZiBv
answer:
oLkWcm

question:
wLLwjL, arLwXm
answer:
Lw

question:
UYyDnXkaZXR, PYRLnXkaZRy
answer:
nXkaZ