Input TRS:
    1: active(zeros()) -> mark(cons(0(),zeros()))
    2: active(tail(cons(X,XS))) -> mark(XS)
    3: mark(zeros()) -> active(zeros())
    4: mark(cons(X1,X2)) -> active(cons(mark(X1),X2))
    5: mark(0()) -> active(0())
    6: mark(tail(X)) -> active(tail(mark(X)))
    7: cons(mark(X1),X2) -> cons(X1,X2)
    8: cons(X1,mark(X2)) -> cons(X1,X2)
    9: cons(active(X1),X2) -> cons(X1,X2)
    10: cons(X1,active(X2)) -> cons(X1,X2)
    11: tail(mark(X)) -> tail(X)
    12: tail(active(X)) -> tail(X)
Number of Rules: 12
Direct QWPOS(Pol) ... failed.