Input TRS:
    1: nats() -> adx(zeros())
    2: zeros() -> cons(0(),zeros())
    3: incr(cons(X,Y)) -> cons(s(X),incr(Y))
    4: adx(cons(X,Y)) -> incr(cons(X,adx(Y)))
    5: hd(cons(X,Y)) -> X
    6: tl(cons(X,Y)) -> Y
Number of Rules: 6
Direct QTKBOS ... failed.