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

Q: wbFDXJQDQxQJzudOUlR, QEbsIDXJQDQxQsSYIutwU

A: DXJQDQxQ
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Q: JIOKyo, oPOKsX

A: OK
****
Q: UFVUYgWuPQA, rGuUYgWoQ

A:
UYgW
****