Vietnamese national Olympiad 2007, problem 4
Source:
February 8, 2007
combinatorics unsolvedcombinatorics
Problem Statement
Given a regular 2007-gon. Find the minimal number such that: Among every vertexes of the polygon, there always exists 4 vertexes forming a convex quadrilateral such that 3 sides of the quadrilateral are also sides of the polygon.