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

Example Input: xzMUdHcoYJFWLOILjrg, vCscoYJFWLzO
Example Output: coYJFWL

Example Input: BmwpAnWJ, klVwpAFw
Example Output: wpA

Example Input: uGLyKbhMMQOPetezozMYUgSf, jVtMQOPetezXhyhXc
Example Output:
MQOPetez