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

Example Input: nuwMzarLqoPvabJla, JKcrLqoPvabJNDCILGQ
Example Output: rLqoPvabJ

Example Input: fdinRdwwlntwqzYGhV, ZefonRdwwlntoWQbh
Example Output: nRdwwlnt

Example Input: DoetrGBh, FretrZi
Example Output:
etr