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: cKsJcqYvZO, UrsJcqBC
Example Output: sJcq

Example Input: osMiZweYXlHrA, cUMiZweYSCKBsX
Example Output:
MiZweY