%!PS-Adobe-2.0

51 1 551
{ /x exch def
  111 1 721
  { /y exch def
    y 521 sub
    201 div
    x 301 sub
    201 div
    1 index
    1 index
    31 -1 1
    { /n exch def
      1 index
      dup mul
      1 index
      dup mul
      1 index
      1 index
      add
      /d exch def
      sub
      4 index add
      3 1 roll
      2 mul mul
      2 index add
      d 4 gt
      {exit} if
    } for
    pop pop pop pop
    n 31 div
    setgray
    x y moveto
    1 0 rlineto
    0 1 rlineto
    -1 0 rlineto
    fill
  } for
} for
showpage