Input TRS:
    1: nats() -> cons(0(),n__incr(nats()))
    2: pairs() -> cons(0(),n__incr(odds()))
    3: odds() -> incr(pairs())
    4: incr(cons(X,XS)) -> cons(s(X),n__incr(activate(XS)))
    5: head(cons(X,XS)) -> X
    6: tail(cons(X,XS)) -> activate(XS)
    7: incr(X) -> n__incr(X)
    8: activate(n__incr(X)) -> incr(X)
    9: activate(X) -> X
Number of Rules: 9
Direct QWPOS(Sum) ... failed.