(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)
        mark(f(X1, X2, X3)) -> active(f(X1, X2, X3))
        mark(g(X)) -> active(g(mark(X)))
        mark(b) -> active(b)
        mark(c) -> active(c)
        f(mark(X1), X2, X3) -> f(X1, X2, X3)
        f(X1, mark(X2), X3) -> f(X1, X2, X3)
        f(X1, X2, mark(X3)) -> f(X1, X2, X3)
        f(active(X1), X2, X3) -> f(X1, X2, X3)
        f(X1, active(X2), X3) -> f(X1, X2, X3)
        f(X1, X2, active(X3)) -> f(X1, X2, X3)
        g(mark(X)) -> g(X)
        g(active(X)) -> g(X)
        
)