painted orthogonal coordinate system
Source: Vietnam TST 2001 for the 42th IMO, problem 5
June 26, 2005
analytic geometryfloor functionceiling functionIMO Shortlistcombinatorics unsolvedcombinatorics
Problem Statement
Let an integer be given. In the space with orthogonal coordinate system we denote by the set of all points with are integers, satisfying the condition: . We paint all the points of in such a way that: if the point is painted then points for which and could not be painted. Find the maximal number of points that we can paint in such a way the above mentioned condition is satisfied.