how do you load a library for all pages in a controller?

[eluser]Abel A.[/eluser]
Lets say I want to load a library in all my pages, how would I do that instead of calling it on each function?

Example:

Code:

class login extends CI_Controller {

public function index()
{
  $this->load->helper('url');
}

public function forgot()
{
  $this->load->helper('url');

}

public function activate()
{
  $this->load->helper('url');
}

}