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

[EX Q]: YWNPkA, LuNPnN
[EX A]: NP

[EX Q]: VLxrvK, gvxrac
[EX A]: xr

[EX Q]: NNpkdhvgT, BMkAkdhvrwV
[EX A]:
kdhv