instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
cvZfWOwa, xOfWOhZs
answer:
fWO

question:
JqdTDnZqSuSVcMsx, TEtDDnZqSuZa
answer:
DnZqSu

question:
gJQjyPvz, JOjyPmO
answer:
jyP