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

Example Input: dReySjyqecU, loSjyqiRl
Example Output: Sjyq

Example Input: BVipiZoGXaWdjmDsxWP, yxppsiYkiZoGXaWdjoDRuKW
Example Output: iZoGXaWdj

Example Input: oYBWPUnUJlESMb, MMWPUnUJlESxTHMKhgKv
Example Output:
WPUnUJlES