IMO Shortlist 1969 problem 20


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2. travnja 2012.
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(FRA 3) A polygon (not necessarily convex) with vertices in the lattice points of a rectangular grid is given. The area of the polygon is S. If I is the number of lattice points that are strictly in the interior of the polygon and B the number of lattice points on the border of the polygon, find the number T = 2S- B  -2I + 2.
Izvor: Međunarodna matematička olimpijada, shortlist 1969