%!
/slw {setlinewidth} def
/ed{exch def} def
/rec{
  /y2 ed /x2 ed /y1 ed /x1 ed
  /x3 x1 x2 mul dup sqrt 2 mul x1 add x2 add div def
  /y3 x1 x3 mul sqrt 2 mul y1 add def
  0.48 slw
  x3 y3 x3 0 360 arc stroke
  0 slw
  gsave
  0 0 1 setrgbcolor
  0 y2 y1 add 2 div y2 y1 sub 2 div -90 90 arc stroke
  grestore
  x3 1 gt{
    x1 y1 x3 y3 x3 y3 x2 y2 rec rec
    } if
  }def

100 50 translate
.48 slw
0 0 moveto 0 693 lineto stroke
346.5 0 346.5 90 180 arc stroke
346.5 693 346.5 180 270 arc stroke
346.5 0 346.5 693 rec
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