instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
CUlMsvov, iflMsSRp
answer:
lMs

question:
TvNVpHLPYjBCeUpyxlzFZ, tgKdPKVYjBCeUpyPK
answer:
YjBCeUpy

question:
XMZYDg, lLZYWR
answer:
ZY