These are a few examples of complete problems.

This is a simple basic problem that asks for a program that computes the difference between integers. It should be a good starting point if you want to learn how the problem format works.

This is a simple example of an interactive problem, where there is no fixed input to process, but the solution instead communicates back and forth with a validator program.

This is a problem that just asks for a program that prints Hello World!. It is a somewhat atypical problem since it does not have any input. This problem also illustrates having problem statements in more than one language.