Google I/O, Google’s developer conference, was so quick to sell out this year that now the only way to get a ticket is to participate in a developer challenge.

Google is calling the contest Last Call for Google I/O. The contest will span 10 challenges, and at the end of each challenge Google will give 10 tickets to winners.

The contest will run from March 16 to March 29, and focus on a different Google product each day. For instance, there are challenges for Android, Chrome and the YouTube API. Each day has two rounds–the first requires participants to answer a series of questions correctly to qualify for round two. Round two is a coding challenge.

If you wanted to get to the conference but missed out, find out more here for a second chance.