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

Example Input: yrIDSuVuQU, UXTSuVuLcch
Example Output: SuVu

Example Input: ssKUiWgGqsXYlFOOc, JDcVTmCgGqsXYlxYE
Example Output: gGqsXYl

Example Input: xOeepmDXmaxG, tiUWNTueepmDXmFH
Example Output:
eepmDXm