class Echo(Input,Print,Stop,Chain) extends Program {
  Print p;
  Stop s;
  Input i;
  method continue(Passive accumulator) {
    s = new Stop(Passive);
    p = new Print(Passive,Chain);
    p.next = s;
    i = new Input(Passive,Chain);
    i.next = p;
    goto i.continue(new 0(Passive));
  }
}