Input TRS:
    1: a__nats() -> cons(0(),incr(nats()))
    2: a__pairs() -> cons(0(),incr(odds()))
    3: a__odds() -> a__incr(a__pairs())
    4: a__incr(cons(X,XS)) -> cons(s(mark(X)),incr(XS))
    5: a__head(cons(X,XS)) -> mark(X)
    6: a__tail(cons(X,XS)) -> mark(XS)
    7: mark(nats()) -> a__nats()
    8: mark(incr(X)) -> a__incr(mark(X))
    9: mark(pairs()) -> a__pairs()
    10: mark(odds()) -> a__odds()
    11: mark(head(X)) -> a__head(mark(X))
    12: mark(tail(X)) -> a__tail(mark(X))
    13: mark(cons(X1,X2)) -> cons(mark(X1),X2)
    14: mark(0()) -> 0()
    15: mark(s(X)) -> s(mark(X))
    16: a__nats() -> nats()
    17: a__incr(X) -> incr(X)
    18: a__pairs() -> pairs()
    19: a__odds() -> odds()
    20: a__head(X) -> head(X)
    21: a__tail(X) -> tail(X)
Number of Rules: 21
Direct POLO(mSum) ... failed.