Middle European Mathematical Olympiad 2021 Problem I-4
Let be an integer. Zagi the squirrel sits at a vertex of a regular -gon. Zagi plans to make a journey of jumps such that in the -th jump, it jumps by edges clockwise, for . Prove that if after jumps Zagi has visited distinct vertices, then after jumps Zagi will have visited all of the vertices.
(Remark. For a real number , we denote by the smallest integer larger or equal to .)