The principle of narrow places

The book is devoted to the search for solving non -standard mathematical problems. It offers a general approach uniting a wide group of known techniques. The presentation is carried out in a relaxed manner. The emphasis is on analysis of examples, on how the principle of narrow places helps to find solutions. More than 30 original tasks of the author were used as examples and tasks for independent solutions. Compared to the second edition, published in 2008, the chapter "How can this be?" And the list of tasks is expanded.
The book is addressed to all lovers of interesting tasks, primarily for high school students, as well as teachers and leaders of mathematical circles.
5th edition, stereotypical