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

Example Input: DFRoMPNDAzNgtLsEPseOzC, qykyPjDAzNgtLsEPYTsNrJaNK
Example Output: DAzNgtLsEP

Example Input: YPeBvuJXaSLLPhKpUQ, ryjPdyuJXaSLLPhIzBeJP
Example Output: uJXaSLLPh

Example Input: RhaEJkwzP, xQkEJkCv
Example Output:
EJk