(VAR x1 )
(RULES 
        b(a(a(x1))) -> a(b(c(x1)))
        c(a(x1)) -> a(c(x1))
        b(c(a(x1))) -> a(b(c(x1)))
        c(b(x1)) -> b(a(x1))
        a(c(b(x1))) -> c(b(a(x1)))
        
)