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

[EX Q]: OXdSmcKG, XbDdSmJl
[EX A]: dSm

[EX Q]: VutZiVkDQcVpQO, BDQVDyBdiVkDQcVpuvNN
[EX A]: iVkDQcVp

[EX Q]: gxxvwyoasSz, JRvwyoasjAXzib
[EX A]:
vwyoas