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:
yhhzISsXKEbA, KlPrazISsXKzmrVBG
answer:
zISsXK


question:
nJjJso, JZjJqG
answer:

jJ