MathDB
ASU 270 All Soviet Union MO 1979 grasshopper hopping on cartesian

Source:

July 11, 2019
coordinatesareascombinatorial geometry

Problem Statement

A grasshopper is hopping in the angle x0,y0x\ge 0, y\ge 0 of the coordinate plane (that means that it cannot land in the point with negative coordinate). If it is in the point (x,y)(x,y), it can either jump to the point (x+1,y1)(x+1,y-1), or to the point (x5,y+7)(x-5,y+7). Draw a set of such an initial points (x,y)(x,y), that having started from there, a grasshopper cannot reach any point farther than 10001000 from the point (0,0)(0,0). Find its area.