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SMO 2019 Open Round 2 Question 3

SMO · SMO 2019 Open Round 2

Question 3

A robot is placed at a point $P$ on the $x$-axis but different from $(0,0)$ and $(1,0)$ and can move only along the axis either to the left or to the right. Two players play the following game. Player $A$ gives a distance and $B$ gives a direction and the robot will move the indicated distance along the indicated direction. Player $A$ aims to move the robot to either $(0,0)$ or $(1,0)$. Player $B$'s aim is to stop $A$ from achieving his aim. For which $P$ can $A$ win?