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

Example Input: yITbYie, TlqTbYomH
Example Output: TbY

Example Input: OjQHcFUCflYUptUPqYKVomn, GXHcFUCflYUpSSTrQ
Example Output: HcFUCflYUp

Example Input: VuXPVv, EoXPPe
Example Output:
XP