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

Example Input: aeQjEeiWGONmzGimhGiw, RIEeiWGONmOZuVYr
Example Output: EeiWGONm

Example Input: eJPZzg, lFPZbI
Example Output: PZ

Example Input: yOUdJq, pcUdKK
Example Output:
Ud