instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
KvPFobZEGs, eKFobZEtnm
answer:
FobZE


question:
rduIwWNGM, AJqYIwWNaCap
answer:
IwWN


question:
BMiENvvoz, LwgaiENvvhNFJn
answer:

iENvv