instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
fVEFJa, WtEFYK
answer:
EF


question:
QvtDqzQiSknPbRCG, hVxHdqzQiSknPbumdpNIf
answer:
qzQiSknPb


question:
fvhCwoVnaz, izAuhCwoVao
answer:

hCwoV