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

Example Input: oiNEYHxbvAb, bcDDdEYHxbCREd
Example Output: EYHxb

Example Input: bUcuzFgsdfojVR, IdcuzFgsdMRgtMA
Example Output: cuzFgsd

Example Input: JElWhwstcISgVvjiaoyK, bLJkDfYCwstcISgVvZnkk
Example Output:
wstcISgVv