The tasks of the St. Petersburg Olympiad for schoolchildren in mathematics in 2021

The book is intended for schoolchildren, teachers, teachers of mathematical circles and just fans of mathematics. The reader will find in it the tasks of the St. Petersburg Olympiad of schoolchildren in mathematics in 2021, as well as the tasks of the open Olympiad of the FML No. 239, which, not being a round of the St. Petersburg Olympiad, by the nature of the tasks, the composition of participants and the venue, is an excellent addition to it.
All tasks are given with detailed solutions, the conditions and solutions of geometric problems are accompanied by drawings.
As an additional material, a selection of the tasks of the Tuymaada Olympiad and two tales about the adventures of Busenka and her friends are given.
The compilers Kokhak K.P., Rostovsky D.A., Khrabrov A.I. and etc