How can I register with python requests in Instagram

I'm writing a program to logging in my Instagram with python requests. It's looks like that:

import requests

# Fill in your details here to be posted to the login form.
payload = {
    'inUserName': 'username',
    'inUserPass': 'password'
}

# Use 'with' to ensure the session context is closed after use.
with requests.Session() as s:
    p = s.post(LOGIN_URL, data=payload)

Later I used headers to make fake user agent too, but at all times it responses <Response 403>.