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

Example Input: UIjAMFDuxDDGkfQa, VdsHuxDDGkfZHZZ
Example Output: uxDDGkf

Example Input: jdLbZSCzaAHGbNwILGmudOH, RdIPuEYJvUZSCzaAHGbNduLToRC
Example Output: ZSCzaAHGbN

Example Input: dYhKIvQWINtnWDjfBhB, WiFETGjCWINtnWDjuDTOKulG
Example Output:
WINtnWDj