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

[EX Q]: cjDuPZOHjystHnF, okWVdUDuPZOHjSCaEecP
[EX A]: DuPZOHj

[EX Q]: OjQHcFUCflYUptUPqYKVomn, GXHcFUCflYUpSSTrQ
[EX A]: HcFUCflYUp

[EX Q]: HbTKzXjU, NuKzXkkc
[EX A]:
KzX