digraph foogrph {
  node [shape = record,height=.1];
  node21[label = "<left> |<center> 21|<right> "];
  "node21":left -> "node20":center;
  node20[label = "<left> |<center> 20|<right> "];
  "node20":left -> "node18":center;
  node18[label = "<left> |<center> 18|<right> "];
  "node18":right -> "node21":center;
  node21[label = "<left> |<center> 21|<right> "];
  "node21":right -> "node19":center;
  node19[label = "<left> |<center> 19|<right> "];
  "node19":left -> "node17":center;
  node17[label = "<left> |<center> 17|<right> "];
  "node19":right -> "node16":center;
  node16[label = "<left> |<center> 16|<right> "];
}