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

[EX Q]: jsXHot, gtXHmB
[EX A]: XH

[EX Q]: bmsrkXGb, GcarkXOZF
[EX A]: rkX

[EX Q]: hXYNzsFxmxdYouTu, pSvNzsFxmxay
[EX A]:
NzsFxmx

