instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
edjRAatlaiCmWkpqMh, qDZYVWCDTRAatlaiCmYH
answer:
RAatlaiCm


question:
yiKkIxbKvNk, znaIxbKggg
answer:
IxbK


question:
IGHhMfqLeBpnullsPInfBH, LTDBpnullsPIBynwCrCQ
answer:

BpnullsPI