Donald is not very good at math.

He couldn't understand the teacher's explanation, even if he repeated it for the second time.

He said to himself, "It doesn't matter. I'm good at other subjects, as long as I cheat in the math exam." He thought, just sit next to the person who is the best at math and copy his answers.

It's the day of the exam. Donald is sitting next to Brian Smith. His math score is usually the best.

Donald carefully copied Brian's answers into his test paper.

After the exam, the teacher put away the test paper and corrected it. Then she said, "Classmates, I decided to give the prize to the student who scored the highest, but it was difficult for me to decide who to give it to, because Donald and Brian scored the same."

A classmate said, "Give it to them and let them share it."

The teacher said, "I thought about doing that, but I decided to give it to Brian."

Donald was very angry and stood up and said, "It's not fair! Brian scored the same as me. "

The teacher said, "Yes, but Brian's answer to question 18 is" I don't know "and your answer is" I don't know (I don't know) ".