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: HXYkGv, GCYksu

Answer: Yk


Question: lypuwWy, jRpuwcE

Answer: puw


Question: btHwjMDgZVAOeaOqcM, nEVWqqVDgZVAOeJNFmO

Answer:
DgZVAOe