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

Example Input: ssKUiWgGqsXYlFOOc, JDcVTmCgGqsXYlxYE
Example Output: gGqsXYl

Example Input: YPeBvuJXaSLLPhKpUQ, ryjPdyuJXaSLLPhIzBeJP
Example Output: uJXaSLLPh

Example Input: zeuyZKwvIOfx, BlmZKwvspUt
Example Output:
ZKwv