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

[EX Q]: AeYjeKwZQillzpD, SnqviKwZQillrxuTB
[EX A]: KwZQill

[EX Q]: hGyDyQYdxCCuD, BQiFOyQYdxel
[EX A]: yQYdx

[EX Q]: ByNApXbE, UBzApXJeR
[EX A]:
ApX