RU-ALLRUSSIAN 1979 Problem 2

A grasshopper hops about in the first quadrant $(\mathrm{x},\mathrm{y}\geqslant = 0)$ . From $(\mathrm{x},\mathrm{y})$ it can hop to $(\mathrm{x} + 1,\mathrm{y} - 1)$ or to $(\mathrm{x} - 5,\mathrm{y} + 7)$ , but it can never leave the first quadrant. Find the set of points $(\mathrm{x},\mathrm{y})$ from which it can never get further than a distance 1000 from the origin.