IMO 1978 LL NET32

Let C be the circumcircle of the square with vertices (0, 0),

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IMO 1978 LL NET32

Origin: NET

Problem

Let C be the circumcircle of the square with vertices (0, 0), (0, 1978), (1978, 0), (1978, 1978) in the Cartesian plane. Prove that C con- tains no other point for which both coordinates are integers.