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

Example Input: JjEQVKijeyEQ, dwSVKijeywCTvb
Example Output: VKijey

Example Input: gfDDsblwUryUw, UWaRisblwUTqTM
Example Output: sblwU

Example Input: GlGZff, ZUGZtX
Example Output:
GZ