@startdot
digraph associative {
  rankdir = RL;
  node [fontsize = 11, shape = circle, style=rounded ];
  s1 [label="博多"];
  s2 [label="小倉"];
  s3 [label="広島"];
  s1 -> s2 [label="f"]
  s2 -> s3 [label="g"]
  s1 -> s3 [label="g∘f"]
}
@enddot