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

Example Input: bjjsMtBzzXIgYWPBZmaDL, iTxktmvBzzXIgYWPhbAyBE
Example Output: BzzXIgYWP

Example Input: sOSXbnluNuvwMETKda, JzXbnluNuvyeVHO
Example Output: XbnluNuv

Example Input: OyGptBaPliWFHBsXSwOk, gJyTkRaPliWFHBsXmcHhwQGuHa
Example Output:
aPliWFHBsX