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

Example Input: dxqZUOvRprXyFfjQfTWBhR, biSVjOvRprXyFfDtuFWQ
Example Output: OvRprXyFf

Example Input: sHndIbPaygfNvnquxIHeteW, huLmJWXZIgfNvnquxIViQDhbuoL
Example Output: gfNvnquxI

Example Input: rfMYLyIdZovqO, uNoVYLyIdDoyL
Example Output:
YLyId