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

class Cat(CatLoop,Input,Print,Chain) extends Program {
  CatLoop a;
  method continue(Passive accumulator) {
    a = new CatLoop(Passive,Chain,Input,Print);
    a.next = a;
    goto a.continue(new 0(Passive));
  }
}