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

Example Input: yRhCObvPZYoKUoQnyaatR, NHzLJYPZYoKUoQnJnIsZxC
Example Output: PZYoKUoQn

Example Input: WFAPUCgVYbmZiFlacUzyv, xQFiekrgPUCgVYbmZUEtl
Example Output: PUCgVYbmZ

Example Input: VXSDosmuJUF, EFsSDosmuJobNz
Example Output:
SDosmuJ