Can't add nginx latest version app repository in ubuntu 14.04

Ubuntu installs nginx 1.4.6 as default. I'm trying to install the lastest stable version of nginx (1.6.2). So here it says:

you need to add Ubuntu PPA repository to get latest stable version of Nginx on your system. use the below commands to do it.

# Add repository to your system
# magesh@magesh-desktop:~$ add-apt-repository ppa:nginx/$nginx

But when I try this command it throws error:

Cannot add PPA: 'ppa:nginx/'.
Please check that the PPA name or format is correct.

How can I solve it?

Thanks

Replace $nginx with stable :

add-apt-repository ppa:nginx/stable
apt-get update
apt-get install nginx