Any five points in the plane contain a convex quadrilateral according to this person’s so-called “happy ending problem.” The Green-Tao theorem proves a specific case of a conjecture named after this person, which states that any substantial set has arbitrarily long arithmetic progressions. This person is the alphabetically first namesake of a model used to generate random graphs (15[2])given a fixed number of nodes and edges. (15[1])Along with George (*) Szekeres (“SEK-eh-resh”), this man proved the first upper bound for Ramsey numbers. This man popularized a technique which proves the existence of objects by showing the chance of choosing them randomly is nonzero called the probabilistic method. For 10 points, name this eccentric Hungarian mathematician whose namesake “number” quantifies distance from him via coauthorship of papers. ■END■