instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
tGBRASi, QABRAtL
answer:
BRA


question:
HiGmCdXrmFRJYWLvZbpU, IxhkrmFRJYWLvZLaqRVxPkL
answer:
rmFRJYWLvZ


question:
OjCSQjbVAYVB, iJRxCSQjbVhHrH
answer:

CSQjbV