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

Example Input: EOacPYivmmUlYenynBqAwx, MoZWMOeXmUlYenynBEendWg
Example Output: mUlYenynB

Example Input: OBzHWjmkcgVGPyv, gCHWjmkcgVMq
Example Output: HWjmkcgV

Example Input: kgUrumyeIFmfWMVJLyXS, XgWEybRqIFmfWMVJTuo
Example Output:
IFmfWMVJ