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

[Q]: goyZUz, QryZlD
[A]: yZ


[Q]: BeEgLISxThm, UGLISxEtP
[A]: LISx


[Q]: RCdsfdFTfd, inUdsfdDX
[A]:
dsfd