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

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

[EX Q]: iupYjFXrrMqWzJSLUSwmEukHc, hqajjWrrMqWzJSLnF
[EX A]: rrMqWzJSL

[EX Q]: AurvWUydTCIyXpG, pyOTfrvWUydTCOEBQPEDZ
[EX A]:
rvWUydTC