% PNAS example 2
% https://www.pnas.org/content/pnas/116/31/15407.full.pdf
% by Vladimir Batagelj, June 17, 2020
*Vertices 13
  1 "A1"     0.1234  0.3056  0.5000  ellipse
  2 "A2"     0.2510  0.3646  0.5000
  3 "A3"     0.3102  0.2125  0.5000
  4 "A4"     0.2080  0.1337  0.5000
  5 "A5"     0.4771  0.2083  0.5000
  6 "A6"     0.4189  0.3507  0.5000
  7 "B1"     0.6588  0.4618  0.5000  diamond
  8 "B2"     0.8322  0.4479  0.5000
  9 "B3"     0.6949  0.5990  0.5000
 10 "B4"     0.8197  0.6233  0.5000
 11 "C1"     0.4549  0.7170  0.5000  box
 12 "C2"     0.3218  0.8681  0.5000
 13 "C3"     0.2247  0.7170  0.5000
*Arcs
  1   2 1
  3   2 1
  3   6 1
  4   3 1
  5   3 1
  5   6 1
  5   7 1
  5   8 1
  6  12 1
  7   6 1
  8  10 1
  9   7 1
  9   8 1
 10  12 1
 11   6 1
 11   9 1
 11  12 1
 12  13 1
 13   2 1
 13  11 1