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

Example Input: yxJxNRLEnKGHziJtfb, KfReWhEnKGHzitzfPWzK
Example Output: EnKGHzi

Example Input: hUpEbyvEcQ, dHpEbyvEvwsXcN
Example Output: pEbyvE

Example Input: hXksmQ, DbksRW
Example Output:
ks