digraph example {
  phone_input [shape=box label="phone"];
  phone_state [shape=doublecircle label="phone"];
  smscode_input [shape=box label="smscode"];
  smscode_state [shape=doublecircle label="smscode"];
  login_state [shape=doublecircle label="login"];

  phone_input -> phone_state -> login_state;
  smscode_input -> smscode_state -> login_state;
}