Yes 556 is correct.
Your need to add your public SSH key which cloud9 provides, this is located here: https://c9.io/account/ssh
Then login to your BitBucket account and goto your account settings (click on your avatar, top right. Then click BitBucket settings)
Then on the left side menu your see SSH Keys link, click that and then add the Cloud9 provided key.
or change this link
Then you should be able to push to your repository.
If you dont want to use SSH keys and just login to bitbucket each time you push you can change the
.git/config file remote url.
url = email@example.com:bitbucket_username/your_repo.git
Change to use HTTPS:
url = https://bitbucket.org/bitbucket_username/your_repo.git
Your then have to login each time you push your changes.
Hope it helps