Input TRS:
    1: active(nats()) -> mark(cons(0(),incr(nats())))
    2: active(pairs()) -> mark(cons(0(),incr(odds())))
    3: active(odds()) -> mark(incr(pairs()))
    4: active(incr(cons(X,XS))) -> mark(cons(s(X),incr(XS)))
    5: active(head(cons(X,XS))) -> mark(X)
    6: active(tail(cons(X,XS))) -> mark(XS)
    7: mark(nats()) -> active(nats())
    8: mark(cons(X1,X2)) -> active(cons(mark(X1),X2))
    9: mark(0()) -> active(0())
    10: mark(incr(X)) -> active(incr(mark(X)))
    11: mark(pairs()) -> active(pairs())
    12: mark(odds()) -> active(odds())
    13: mark(s(X)) -> active(s(mark(X)))
    14: mark(head(X)) -> active(head(mark(X)))
    15: mark(tail(X)) -> active(tail(mark(X)))
    16: cons(mark(X1),X2) -> cons(X1,X2)
    17: cons(X1,mark(X2)) -> cons(X1,X2)
    18: cons(active(X1),X2) -> cons(X1,X2)
    19: cons(X1,active(X2)) -> cons(X1,X2)
    20: incr(mark(X)) -> incr(X)
    21: incr(active(X)) -> incr(X)
    22: s(mark(X)) -> s(X)
    23: s(active(X)) -> s(X)
    24: head(mark(X)) -> head(X)
    25: head(active(X)) -> head(X)
    26: tail(mark(X)) -> tail(X)
    27: tail(active(X)) -> tail(X)
Number of Rules: 27
Direct POLO(mSum) ... failed.