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

Example Input: osmJJcZlDAXBgJFsJKa, rzPNlDAXBgJYrgXlH
Example Output: lDAXBgJ

Example Input: ylyLVUjsmMrXMFAPDGIZsHq, cYymMrXMFAPjm
Example Output: mMrXMFAP

Example Input: ssKUiWgGqsXYlFOOc, JDcVTmCgGqsXYlxYE
Example Output:
gGqsXYl