Who said that you need to write boring and tedious about mathematics? Who said that a textbook written with a claim to be read is nonsense? Even the creators of the most impenetrable courses admitted that a mathematical text deprived of freedom of speech risks becoming pedantic and difficult to read. The author of an ideal mathematics textbook should be imagined as a person with a piece of chalk, and the text of the book should be a living story that is born here and now and is interrupted by calculations on the board.