instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
BTvLVMYp, mjOvLVMqYo
answer:
vLVM


question:
atDgsOWuP, UJMgsOrwj
answer:
gsO


question:
OnXKagDJwlTZ, KxKagDJPVP
answer:

KagDJ