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

[EX Q]: TdvkBvVyJcSdYGGPfnyml, rIvIvVyJcSdYhtxG
[EX A]: vVyJcSdY

[EX Q]: mjCEUoPmeKbvCgUtUL, SrHtrPmeKbvYpQAVp
[EX A]: PmeKbv

[EX Q]: XSaCcYtHDQkhJnDMqbe, WXEwYHDQkhJnDonu
[EX A]:
HDQkhJnD