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

Example Input: vMsEJRoLkWcmkuwNRz, ZmoLkWcmVZiBv
Example Output: oLkWcm

Example Input: OXdSmcKG, XbDdSmJl
Example Output: dSm

Example Input: cbscpjXUUKJnikIOzM, RFtZpjXUUKJnFZpG
Example Output:
pjXUUKJn