int grid[8][8] =
{ { 6, 0, 0, 0, 0, 3, 0, 4, 0 },
  { 0, 3, 0, 0, 0, 0, 5, 0, 9 },
  { 0, 0, 0, 0, 1, 0, 8, 0, 0 },
  { 0, 0, 0, 0, 8, 0, 9, 0, 3 },
  { 0, 6, 0, 0, 9, 0, 0, 2, 0 },
  { 1, 0, 3, 0, 5, 0, 0, 0, 0 },
  { 0, 0, 5, 0, 3, 0, 0, 0, 0 },
  { 2, 0, 4, 0, 0, 0, 0, 5, 0 },
  { 0, 8, 0, 4, 0, 0, 0, 0, 1 } };