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

Example Input: HSsyZzZLZAAq, MFEZzZLJC
Example Output: ZzZL

Example Input: lMRuEThD, wqQRuEKp
Example Output: RuE

Example Input: NnFTJSbZu, IlTJSXWk
Example Output:
TJS