O(1) - be dangerous at competitive programming

There is no secret that the best way to improve your programming skills is to practice and just practice. O (1) - will be useful by the archive of tasks, conveniently sorted by complexity and topics. If you have long dreamed to be programmer, but did not started, you must to pay attention to this application.

This app has three blocks:
1) Block of interesting tasks that will help you raise your programming skill.
2) Contests Calendar - find out about all future contests in our application.
3) Explor block - searching for tasks by category.

Problems archive is from site codeforces.com