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

Example Input: XbjDHRCWxdPbhibUKn, SrpuPDHRCWxdPbKPWEXNWbZ
Example Output: DHRCWxdPb

Example Input: oUEcuLINTDdvdOne, thzWccuLINTDQfNZwH
Example Output: cuLINTD

Example Input: JGAPubtDyFrKJvyvNIRoF, RssbtDyFrKJmYxnAizO
Example Output:
btDyFrKJ