ISL 1991 Problem 9
In the plane we are given a set of 1991 points, and certain pairs of these points are joined with a path. We suppose that for every point of there exist at least 1593 other points of to which it is joined by a path. Show that there exist six points of every pair of which are joined by a path.
Alternative version: Is it possible to find a set of 1991 points in the plane and paths joining certain pairs of the points in such that every point of is joined with a path to at least 1592 other points of and in every subset of six points of there exist at least two points that are not joined?
Dataset text AI-MO AoPS. Quoted with source.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.
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