(VAR X X1 X2 X3 Y )
(RULES 
        a__f(X, g(X), Y) -> a__f(Y, Y, Y)
        a__g(b) -> c
        a__b -> c
        mark(f(X1, X2, X3)) -> a__f(X1, X2, X3)
        mark(g(X)) -> a__g(mark(X))
        mark(b) -> a__b
        mark(c) -> c
        a__f(X1, X2, X3) -> f(X1, X2, X3)
        a__g(X) -> g(X)
        a__b -> b
        
)