Can't run gunicorn on port 80 while deploying django app on AWS EC2

I am running Ubuntu 14.04 instance in my EC2 AWS.

I can run gunicorn -b 0.0.0.0:8000 myapp.wsgi

but it fails to run at port 80

gunicorn -b 0.0.0.0:80 myapp.wsgi --> Fails

I tried to follow this answer (I couldn't understand it though, whats deployment script ?) Getting Gunicorn to run on port 80

But it didn't work.

I also tried running it with elevated permission sudo in vain.