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

[EX Q]: cxYVucnmEQopeWHrPJ, jNnOaYVucnmEQoSE
[EX A]: YVucnmEQo

[EX Q]: oZNKLmfxecDfkXEGFkRBYk, tReqkiExecDfkXEGtNZpJVRxC
[EX A]: xecDfkXEG

[EX Q]: zsgAkpUxwPLhvLMp, ujkkpUxwPLhNsmQJ
[EX A]:
kpUxwPLh