(STRATEGY
    INNERMOST)

(VAR
    X X1 X2 Y)
(DATATYPES
    A = µX.< mark(X), nil, 0, ok(X) >)
(SIGNATURES
    active :: [A] -> A
    from :: [A] -> A
    cons :: [A x A] -> A
    s :: [A] -> A
    proper :: [A] -> A
    length :: [A] -> A
    length1 :: [A] -> A
    top :: [A] -> A)
(RULES
    active(from(X)) -> mark(cons(X
                                ,from(s(X))))
    active(length(nil())) ->
      mark(0())
    active(length(cons(X,Y))) ->
      mark(s(length1(Y)))
    active(length1(X)) ->
      mark(length(X))
    active(from(X)) ->
      from(active(X))
    active(cons(X1,X2)) ->
      cons(active(X1),X2)
    active(s(X)) -> s(active(X))
    from(mark(X)) -> mark(from(X))
    cons(mark(X1),X2) ->
      mark(cons(X1,X2))
    s(mark(X)) -> mark(s(X))
    proper(from(X)) ->
      from(proper(X))
    proper(cons(X1,X2)) ->
      cons(proper(X1),proper(X2))
    proper(s(X)) -> s(proper(X))
    proper(length(X)) ->
      length(proper(X))
    proper(nil()) -> ok(nil())
    proper(0()) -> ok(0())
    proper(length1(X)) ->
      length1(proper(X))
    from(ok(X)) -> ok(from(X))
    cons(ok(X1),ok(X2)) ->
      ok(cons(X1,X2))
    s(ok(X)) -> ok(s(X))
    length(ok(X)) -> ok(length(X))
    length1(ok(X)) -> ok(length1(X))
    top(mark(X)) -> top(proper(X))
    top(ok(X)) -> top(active(X)))