instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ylyLVUjsmMrXMFAPDGIZsHq, cYymMrXMFAPjm
answer:
mMrXMFAP

question:
QzJdafaGRLWEguLkOaw, brmPLBoaGRLWEguEaF
answer:
aGRLWEgu

question:
BadNgr, iTdNSf
answer:
dN