(VAR x1 )
(RULES 
        a(a(x1)) -> b(c(x1))
        b(b(x1)) -> c(d(x1))
        b(x1) -> a(x1)
        c(c(x1)) -> d(f(x1))
        d(d(x1)) -> f(f(f(x1)))
        d(x1) -> b(x1)
        f(f(x1)) -> g(a(x1))
        g(g(x1)) -> a(x1)
        
)