This book represents an introductory course of Calculus. The course evolved from the lectures, which the author had given in the Kolmogorov School in years 1986-1998 for the one-year stream. The Kolmogorov School is a special physicsmathematical undergraduate school for gifted children. Most of the graduates of Kolmogorov School continue their education in Moscow University, where they have to learn the Calculus from the beginning.