How to find the username of the instance launched in amazon-ec2?

I m having trouble connecting to amazon ec2 instance using ssh. The key pair matches. On google-ing a bit i find that username is not the same for all instances. I assumed its always ec2-user. How can I find the username of the instance that I have launched?

I am getting this error:

Permission denied (publickey).

on trying this:

ssh -i test-instance.pem  ec2-user@23.22.214.148

Any help will be appreciated.