In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

[Q]: OXdSmcKG, XbDdSmJl
[A]: dSm


[Q]: DGvUCrUVlUnQBShkWnfnceGasvI, NfzGUnQBShkWnpLMnY
[A]: UnQBShkWn


[Q]: BefNhv, bzfNOz
[A]:
fN