2007 OIM Problems/Problem 4

Problem

On a $19 \times 19$ grid board, a piece called a "dragon" jumps from side to side in the following way: it moves 4 squares in a direction parallel to one of the sides of the board and 1 square in a direction perpendicular to the previous one. It is known that, with this type of jumps, the dragon can move from any square to any other. The dragonian distance between two squares is the fewest number of jumps the dragon must take to move from one square to another. Let $C$ be a square located in a corner of the board and let $V$ be the square next to $C$ that touches a single point. Prove that there is some square $X$ on the board such that the dragonian distance from $C$ to $X$ is greater than the dragonian distance from $C$ to $V$.

~translated into English by Tomas Diaz. ~orders@tomasdiaz.com

Solution

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See also

OIM Problems and Solutions