{ "domain": "mathematics", "topics": [ "discrete-geometry", "combinatorics" ], "type": "construction", "also": [ "proof" ], "cover": { "motif": "points", "n": 9 }, "source": { "key": "erdos", "name": "Erdős Problems", "url": "https://www.erdosproblems.com/107", "id": "107", "curator": "Thomas Bloom", "poser": "Paul Erdős, Esther Klein and George Szekeres", "status": "open, $500 prize", "as_of": "2026-10-20", "prize": "$500", "catalog": "0521c19bbd38" } }