MAYBE MAYBE TRS: { mark(cons(X1, X2)) -> active(cons(mark(X1), X2)), mark(0()) -> active(0()), mark(zeros()) -> active(zeros()), mark(and(X1, X2)) -> active(and(mark(X1), X2)), mark(tt()) -> active(tt()), mark(length(X)) -> active(length(mark(X))), mark(nil()) -> active(nil()), mark(s(X)) -> active(s(mark(X))), cons(X1, mark(X2)) -> cons(X1, X2), cons(X1, active(X2)) -> cons(X1, X2), cons(mark(X1), X2) -> cons(X1, X2), cons(active(X1), X2) -> cons(X1, X2), active(zeros()) -> mark(cons(0(), zeros())), active(and(tt(), X)) -> mark(X), active(length(cons(N, L))) -> mark(s(length(L))), active(length(nil())) -> mark(0()), and(X1, mark(X2)) -> and(X1, X2), and(X1, active(X2)) -> and(X1, X2), and(mark(X1), X2) -> and(X1, X2), and(active(X1), X2) -> and(X1, X2), length(mark(X)) -> length(X), length(active(X)) -> length(X), s(mark(X)) -> s(X), s(active(X)) -> s(X) } DUP: We consider a non-duplicating system. Trs: { mark(cons(X1, X2)) -> active(cons(mark(X1), X2)), mark(0()) -> active(0()), mark(zeros()) -> active(zeros()), mark(and(X1, X2)) -> active(and(mark(X1), X2)), mark(tt()) -> active(tt()), mark(length(X)) -> active(length(mark(X))), mark(nil()) -> active(nil()), mark(s(X)) -> active(s(mark(X))), cons(X1, mark(X2)) -> cons(X1, X2), cons(X1, active(X2)) -> cons(X1, X2), cons(mark(X1), X2) -> cons(X1, X2), cons(active(X1), X2) -> cons(X1, X2), active(zeros()) -> mark(cons(0(), zeros())), active(and(tt(), X)) -> mark(X), active(length(cons(N, L))) -> mark(s(length(L))), active(length(nil())) -> mark(0()), and(X1, mark(X2)) -> and(X1, X2), and(X1, active(X2)) -> and(X1, X2), and(mark(X1), X2) -> and(X1, X2), and(active(X1), X2) -> and(X1, X2), length(mark(X)) -> length(X), length(active(X)) -> length(X), s(mark(X)) -> s(X), s(active(X)) -> s(X) } Fail