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

Ex Input:
zqwhMdAdXQfQCAmVNaYZm, toYMIwQeadAdXQfQCAmLyheFOv

Ex Output:
dAdXQfQCAm

Ex Input:
HhBhJMpxpty, MxTJMpxnQEf

Ex Output:
JMpx

Ex Input:
xEbUyyFLHrVGgE, HJuXATbUyyFLHivf

Ex Output:
bUyyFLH