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

Example Input: sEYtoQlG, XIstoQQPw
Example Output: toQ

Example Input: JAGuNgaUudP, eojvKNgaUuQg
Example Output: NgaUu

Example Input: UnCZhlAnPg, JKtChlAnAkUR
Example Output:
hlAn