Problem:
 nats() -> adx(zeros())
 zeros() -> cons(0(),zeros())
 incr(cons(X,Y)) -> cons(s(X),incr(Y))
 adx(cons(X,Y)) -> incr(cons(X,adx(Y)))
 hd(cons(X,Y)) -> X
 tl(cons(X,Y)) -> Y

Proof:
 Containment Processor: loop length: 1
                        terms:
                         zeros()
                        context: cons(0(),[])
                        substitution:
                         
  Qed