Description:This book is designed for students and coaches preparing for high-school-level mathematical Olympiads, national or international.The book consists of 23 chapters, each covering a topic in algebra, number theory, or combinatorics. Each chapter has two parts: a "theory and examples" section that presents the main theoretical results of the topic (with proofs if necessary) and 10-15 example problems, and a "problems for training" section with more difficult problems to challenge the reader. (Solutions to the problems in these latter sections are not provided.)