The best books for Olympiad mathematics?

Question

Mathematics

I am in the 10th grade, in a regular school, but in a mat class. Mathematics is given to me very easily, stably 11-12 points (sometimes I make stupid mistakes, for example: 36/13=3, the root of 8=2, or I can add up incorrectly). But I understand the material right away and from the first time, I solve complex problems. On Saturdays I go to courses at the KPI at FPM (Faculty of Applied Mathematics). But then I decided that I need to learn something more than school material, I want to solve the Olympiad task. There is experience in Olympiads in mathematics and physics, prizes in the field.
Recommend a book for learning olympiad problems from mathematics.
Thanks in advance