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

Example Input: cjDuPZOHjystHnF, okWVdUDuPZOHjSCaEecP
Example Output: DuPZOHj

Example Input: uqazNuZhdJhw, KbnrzNuZhBdp
Example Output: zNuZh

Example Input: eefcwRLsaFGBqCQf, omQvMwRLsaFOtQ
Example Output:
wRLsaF