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

[Q]: cUCQXEFSgRZjK, RYdvUQXEFSgRZVlwx
[A]: QXEFSgRZ


[Q]: atDgsOWuP, UJMgsOrwj
[A]: gsO


[Q]: psmfed, jxmfBC
[A]:
mf