8 and 9 can be the same as * * * instead of 3 and 6.

Now there are only five, seven, eight and nine left.

Multiply to get 2520.

The smallest five digits in the multiple of 2520 are 10080.

2, the original odd score, through 30 questions, each question is added and subtracted.

Odd score, the final score is odd score. With odd bits and the same

Learning, odd * odd = odd.

3.{ Single or ~ ~}

4. Use your extension method.