将控制器父类放在CakePHP中的位置？

I have two controllers which share most of their code (but must be, nonetheless, different controllers). The obvious solution (to me, at least) is to create a class, and make the two controllers inherit from it. The thing is... where to put it? Now I have it in app_controller.php, but it's kind of messy there.I have two controllers which share most of thei