The book contains problems in mathematics from the section "Quanta problem book" for the period from 1983 to 1994. The tasks are difficult, most of them much more difficult than exercises from school textbooks and student benefits. Many tasks were offered at olympiads of various levels. Almost all tasks are given brief instructions or answers. For high school students who are passionate about mathematics, teachers of schools, lyceums and gymnasiums, leaders of mathematical circles and electives, as well as for all those who like to solve difficult problems.