.PS
  circle rad 0.1; "0.1" at last circle+(0,-0.2) 
  circle rad 0.2 "0.2" at last circle + (1,0)
  circle rad 0.3 "0.3" at last circle + (1,0)
  move to (0,last circle.s.y-0.4)
  arrow
  box "Input"
  arrow
  box "process"
  arrow
  box "output"
  arrow

  move to (0, 1st arrow.y-0.75)
  {"0.1" at Here+(0,-0.2)}
  arc rad 0.1
  move to last arc.start+(1,0); right
  {"0.2" at Here+(0,-0.2)}
  arc rad 0.2
  move to last arc.start+(1,0); right
  {"0.3" at Here+(0,-0.2)}
  arc rad 0.3
.PE
