(VAR N X X1 X2 XS Y )
(RULES 
        active(fib(N)) -> mark(sel(N, fib1(s(0), s(0))))
        active(fib1(X, Y)) -> mark(cons(X, fib1(Y, add(X, Y))))
        active(add(0, X)) -> mark(X)
        active(add(s(X), Y)) -> mark(s(add(X, Y)))
        active(sel(0, cons(X, XS))) -> mark(X)
        active(sel(s(N), cons(X, XS))) -> mark(sel(N, XS))
        active(fib(X)) -> fib(active(X))
        active(sel(X1, X2)) -> sel(active(X1), X2)
        active(sel(X1, X2)) -> sel(X1, active(X2))
        active(fib1(X1, X2)) -> fib1(active(X1), X2)
        active(fib1(X1, X2)) -> fib1(X1, active(X2))
        active(s(X)) -> s(active(X))
        active(cons(X1, X2)) -> cons(active(X1), X2)
        active(add(X1, X2)) -> add(active(X1), X2)
        active(add(X1, X2)) -> add(X1, active(X2))
        fib(mark(X)) -> mark(fib(X))
        sel(mark(X1), X2) -> mark(sel(X1, X2))
        sel(X1, mark(X2)) -> mark(sel(X1, X2))
        fib1(mark(X1), X2) -> mark(fib1(X1, X2))
        fib1(X1, mark(X2)) -> mark(fib1(X1, X2))
        s(mark(X)) -> mark(s(X))
        cons(mark(X1), X2) -> mark(cons(X1, X2))
        add(mark(X1), X2) -> mark(add(X1, X2))
        add(X1, mark(X2)) -> mark(add(X1, X2))
        proper(fib(X)) -> fib(proper(X))
        proper(sel(X1, X2)) -> sel(proper(X1), proper(X2))
        proper(fib1(X1, X2)) -> fib1(proper(X1), proper(X2))
        proper(s(X)) -> s(proper(X))
        proper(0) -> ok(0)
        proper(cons(X1, X2)) -> cons(proper(X1), proper(X2))
        proper(add(X1, X2)) -> add(proper(X1), proper(X2))
        fib(ok(X)) -> ok(fib(X))
        sel(ok(X1), ok(X2)) -> ok(sel(X1, X2))
        fib1(ok(X1), ok(X2)) -> ok(fib1(X1, X2))
        s(ok(X)) -> ok(s(X))
        cons(ok(X1), ok(X2)) -> ok(cons(X1, X2))
        add(ok(X1), ok(X2)) -> ok(add(X1, X2))
        top(mark(X)) -> top(proper(X))
        top(ok(X)) -> top(active(X))
        
)