Estonian Math Competitions 2005/2006
Source: Seniors Problem 1
July 30, 2008
combinatorics unsolvedcombinatorics
Problem Statement
All the streets in a city run in one of two perpendicular directions, forming unit
squares. Organizers of a car race want to mark down a closed race track in the city in such a way that it would not go through any of the crossings twice and that the track would turn 90◦ right or left at every crossing. Find all possible values of the length of the track.