instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
hUpEbyvEcQ, dHpEbyvEvwsXcN
answer:
pEbyvE


question:
zgJGhxLU, EwJGhedW
answer:
JGh


question:
IQyAgCcdxsZkcZkhq, IUqcdxsZkcZJlySRYM
answer:

cdxsZkcZ