How difficult is the high school math contest?
I once participated in the national high school math competition. The topic of the preliminary contest is more difficult than the last question in any school's mathematics public exam. I suggest you buy a high school math contest, which has many examples. The goal of the preliminary contest is to make 50% people unable to understand the meaning of the topic and 99% people unable to know how to solve the problem. Only one percent of people can do it.