First of all, I published an article in the undergraduate stage. If it is a core journal article, it will increase the tutor's goodwill towards you in the second interview. Not to mention winning prizes and ranking in college students' mathematics competitions. Generally speaking, these things show that you have a solid foundation in mathematics, unlike others who only play during college and delay their studies, which shows the good quality of a prospective graduate student.

Secondly, is the topic you are talking about the exam topic of the math contest? If so, it is certain that there are some differences, but one principle remains unchanged. These topics only have different emphases, but they all need to be based on learning books well. I suggest you read more mathematics counseling materials and real questions related to the postgraduate entrance examination, find out the rules, sum up well, find out the key and common test sites, and combine the experience in the competition, I think you can get good results in the postgraduate entrance examination.

Finally, I would like to remind you that it is a little thin to go to the postgraduate entrance examination just because you are good at math. English is the key to decide whether you can go to graduate school or not, and mathematics is used to grade.

In fact, the Chinese Academy of Sciences is not as difficult as you think. Many universities are national key universities. Shunsong!