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

[EX Q]: yrIDSuVuQU, UXTSuVuLcch
[EX A]: SuVu

[EX Q]: Owbiay, exbime
[EX A]: bi

[EX Q]: wlFcxOHoXC, IWFcxOIWTk
[EX A]:
FcxO