%!PS-Adobe-3.0 EPSF-3.0
/fun {4 3 roll dup dup mul 5 4 roll dup dup mul 2 index exch sub 6 1 roll 2 index
2 mul mul 6 1 roll pop pop 4 1 roll dup 5 1 roll add 4 1 roll 1 index add 4 3 roll exch 4 2 roll} def
/res 700 def /iter 500 def 300 300 translate 90 rotate -150 -260 translate
0 1 res {/x exch def 0 1 res {/y exch def 0 0 -2.5 4 x mul res div add 2 4 y mul res div sub
iter -1 0 {/n exch store fun 2 index dup mul 4 index dup mul add sqrt 4 gt {exit} if} for
pop pop pop pop n 0 gt {1 setgray x y 0.7 0 360 arc fill} {0 setgray x y 0.5 0 360 arc fill} ifelse} for}for
