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

[Q]: VLxrvK, gvxrac
[A]: xr


[Q]: xtCJGe, DXCJSw
[A]: CJ


[Q]: zHTnUQgxyuWYK, EbuEQgxyufPF
[A]:
Qgxyu