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

Q: LudFxiaqbX, UWMPnFxiaqikiDx

A: Fxiaq
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Q: wnIFoRQvMMKMAqpCQYncuWUTJs, bPMUKKxYRxQvMMKMAqpCmzAPPMD

A: QvMMKMAqpC
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Q: ZYAigIGQCHcZwo, vbegIGQCDIbT

A:
gIGQC
****