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

Answer: chtNymcsw


Question: YWNPkA, LuNPnN

Answer: NP


Question: RRRCZG, XrRCzc

Answer:
RC