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

Example Input: XSnVeAjWLFWTgwmf, WsByLAjWLFWnQfl
Example Output: AjWLFW

Example Input: EJZYVxgFxPoOSDlLfK, uTLTIETHZYVxgFxPoPwr
Example Output: ZYVxgFxPo

Example Input: mUBlllktNpzy, ExMllktHP
Example Output:
llkt