instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
apGMPThLTCw, LvMPThYW
answer:
MPTh


question:
bVlwKYBYmcNq, hBlwKYBprL
answer:
lwKYB


question:
ZgOWfOJlgwEWUGG, tcJlgwEWulHMb
answer:

JlgwEW