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

[EX Q]: OrcQOvMBhmwP, mnWrzcQOvMBnLwI
[EX A]: cQOvMB

[EX Q]: jLbHvZmecfxMcGLXGVsO, erFBGmecfxMcJtDyKGZ
[EX A]: mecfxMc

[EX Q]: fzRxrf, JWRxYU
[EX A]:
Rx