Demo fetches the first problem in each language track.

Fetch retrieves problems from the API.

Submit posts code to the API.

Unsubmit deletes a submission.

UserAgent lets the API know where the call is being made from.

Iteration represents a version of a particular exercise.

PayloadError represents an error message from the API.

PayloadProblems represents a response containing problems.

PayloadSubmission represents metadata about a successful submission.

Problem represents a specific problem in a given language track.

Submission is an iteration that has been submitted to the API.