instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
lOedgdw, aoedgpn
answer:
edg


question:
vMYfFo, EHYfnP
answer:
Yf


question:
RvSJiXmOSMMERBaBOiQnO, YCMMERBaBOiQWyTakpDXyZ
answer:

MMERBaBOiQ