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: YRLHFm, odLHCI
Example Output: LH

Example Input: yrIDSuVuQU, UXTSuVuLcch
Example Output:
SuVu