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]: AxAmDG, LTAmEV
[EX A]: Am

[EX Q]: ITQPDUyiUphjT, VrpGVRQPDUyiUZyuaW
[EX A]:
QPDUyiU