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

Example Input: trHTzJpm, aCHTzVVA
Example Output: HTz

Example Input: dReySjyqecU, loSjyqiRl
Example Output: Sjyq

Example Input: rSUpSncS, hnUpSnSvN
Example Output:
UpSn