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

Example Input: wNiHcaiUPHnjp, aSTmjcaiUPHFzOu
Example Output: caiUPH

Example Input: TdvkBvVyJcSdYGGPfnyml, rIvIvVyJcSdYhtxG
Example Output: vVyJcSdY

Example Input: qlTyfAAqKNVwMT, EBycMjvyfAAqKNVlfFgTjz
Example Output:
yfAAqKNV