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

Example Input: VXSNlHzkB, EoNlHCiL
Example Output: NlH

Example Input: jFVaEHbMrrkW, ekfVaEHbPnBnM
Example Output: VaEHb

Example Input: BuuAgFlZkop, tLVAgFlZizgwg
Example Output:
AgFlZ