How to load data from the garter in django-admin?

There Are In The Country. Each country has their city. Must be done so that when the user would select a country in the admin, a gun in the other select(html tag) loaded his city.
In General, this option is no good to me.:
models.py

class Slider(models.Model):
 country = models.ForeignKey(Country, verbose_name="Country")
 city = models.ForeignKey(City, verbose_name="City")
 description = models.TextField(verbose_name="Description")
 status = models.BooleanField(verbose_name="Status")

or create an empty select in forms.py and intercept pattern change_form.html to have it via ajax to load in an empty selekst created in forms.py
Are there any other ways how to do it ?