You can take the format of urionlinejudge.com.br
to understand how the problems are. This means that the description of the problem(problem statement) will be given. For what inputs, what should be the outputs, will be given. As an example, you can see the following problem.
* Keeping in mind that the output format will have to be exactly like the format given. "Wrong Answer" verdict can come even if a new line or space is printed more or less.