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

[EX Q]: QKlzsmHyBcC, snPtzsmHdMIv
[EX A]: zsmH

[EX Q]: UtUSmsOI, dCUSmGoQ
[EX A]: USm

[EX Q]: MvgNlzFKJ, JGNlzFuWYH
[EX A]:
NlzF