(VAR X Y X1 X2 X3)
(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
)