validation rules from 1 to 9

[eluser]aktosci[/eluser]
I would like to check a value from 1 ( min ) to 9 ( max ) :

I did that

Code:

$this->form_validation->set_rules('licoef', 'coef', 'integer'|'exact_length[1]');

but when I put 12 I don't get an error message