(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))
        mark(fib(X)) -> active(fib(mark(X)))
        mark(sel(X1, X2)) -> active(sel(mark(X1), mark(X2)))
        mark(fib1(X1, X2)) -> active(fib1(mark(X1), mark(X2)))
        mark(s(X)) -> active(s(mark(X)))
        mark(0) -> active(0)
        mark(cons(X1, X2)) -> active(cons(mark(X1), X2))
        mark(add(X1, X2)) -> active(add(mark(X1), mark(X2)))
        fib(mark(X)) -> fib(X)
        fib(active(X)) -> fib(X)
        sel(mark(X1), X2) -> sel(X1, X2)
        sel(X1, mark(X2)) -> sel(X1, X2)
        sel(active(X1), X2) -> sel(X1, X2)
        sel(X1, active(X2)) -> sel(X1, X2)
        fib1(mark(X1), X2) -> fib1(X1, X2)
        fib1(X1, mark(X2)) -> fib1(X1, X2)
        fib1(active(X1), X2) -> fib1(X1, X2)
        fib1(X1, active(X2)) -> fib1(X1, X2)
        s(mark(X)) -> s(X)
        s(active(X)) -> s(X)
        cons(mark(X1), X2) -> cons(X1, X2)
        cons(X1, mark(X2)) -> cons(X1, X2)
        cons(active(X1), X2) -> cons(X1, X2)
        cons(X1, active(X2)) -> cons(X1, X2)
        add(mark(X1), X2) -> add(X1, X2)
        add(X1, mark(X2)) -> add(X1, X2)
        add(active(X1), X2) -> add(X1, X2)
        add(X1, active(X2)) -> add(X1, X2)
        
)