If you are a beginner, it is recommended to use excellent training courses to lay the foundation (trial). That book is closely related to the college entrance examination and has been improved. Only by doing it systematically can we have a good foundation.

If you have a strong personal ability and a good foundation, you can also use the course of Olympic Mathematics directly. The advantage of that book is that it has more knowledge points and more difficult topics. It is suitable to read it several times, solve the last problem every time, and try to give some new solutions.

No matter which competition book you use, it is important to make a good summary. Try not to look at the answer to the question. If you can't do it, you can think more or be free first, and then you may be suddenly enlightened.

Hehe, I'm also having a math contest. I'm sent to Nankai University and I'm going to Tianjin this summer.

Wish you success!