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

Example Input: iYSNsY, HSSNhP
Example Output: SN

Example Input: DwLGzwYOWjtzIunE, TTViSbkwYOWjtzNqUOOz
Example Output: wYOWjtz

Example Input: ahPbomjSH, rBbomynK
Example Output:
bom