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

Q: jXbgnl, lUbglP

A: bg
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Q: njzfcapS, JDzfcYQh

A: zfc
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Q: UKsHJBHKRrnQxjsuEclaUBNKOn, GgQUDdeRrnQxjsuEZOKOc

A:
RrnQxjsuE
****