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

[EX Q]: pySBCdpe, AEBCdOR
[EX A]: BCd

[EX Q]: qQkmYsYN, UhkmYHSy
[EX A]: kmY

[EX Q]: YGuQYlZN, JIQYluk
[EX A]:
QYl

