(VAR X X1 X2 X3 Y )
(RULES 
        active(f(X, g(X), Y)) -> mark(f(Y, Y, Y))
        active(g(b)) -> mark(c)
        active(b) -> mark(c)
        active(g(X)) -> g(active(X))
        g(mark(X)) -> mark(g(X))
        proper(f(X1, X2, X3)) -> f(proper(X1), proper(X2), proper(X3))
        proper(g(X)) -> g(proper(X))
        proper(b) -> ok(b)
        proper(c) -> ok(c)
        f(ok(X1), ok(X2), ok(X3)) -> ok(f(X1, X2, X3))
        g(ok(X)) -> ok(g(X))
        top(mark(X)) -> top(proper(X))
        top(ok(X)) -> top(active(X))
        
)