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

[Q]: BrDGrTD, PBHDGrDw
[A]: DGr


[Q]: UtUSmsOI, dCUSmGoQ
[A]: USm


[Q]: smgEmtXfMoYOi, NTZjhmtXfMoTwEVk
[A]:
mtXfMo