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