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

[Q]: OUNqomxFcLXhWdfB, gdqomxFcLHQPCu
[A]: qomxFcL


[Q]: XWKEpwGRkfCFZGOyZQOoypx, lhQkmVqeRkfCFZGOyugPLqs
[A]: RkfCFZGOy


[Q]: kGbkhe, lVbkxk
[A]:
bk