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