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

CxwZWv, mkwZgM
wZ

RtAchtNymcswVk, FWRuRchtNymcswUkoERHyML
chtNymcsw

SBtjzaFYycTcFbKIJQ, lAvkhhYycTcFbKIjjiiD

YycTcFbKI