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

Example Input: euQWhCovKplukMYznXcD, XAfMhKdzhCovKplukMcMlSuBw
Example Output: hCovKplukM

Example Input: GlAYDsKQoXy, IxDsKQuK
Example Output: DsKQ

Example Input: rgufOWpSThBHnYBDJmqnlZyJW, MztnyuUSThBHnYBDJTdbEaJdp
Example Output:
SThBHnYBDJ