I think you should treat a code-golf challenge almost the same as a task or project your boss wants you to work on.
If the language you want to use to solve this task isn't appropriate, I suppose you won't ask your boss to adjust the project, to fit to your preferred programming language.
Instead, you'll choose an appropriate language, to solve the problem fast and elegant.
The other possibility, much easier on Codegolf.SE than explaining to your boss, would be to accept the challenge, deal with the pitfalls of your preferred language, and perhaps come up with a solution you never thougt about before, just to compensate some weird input/output mechanisms.
So, as long as the problem doesn't specify the language it wants to be solved in, it's your choice.
alertfor output and
promptfor input ? \$\endgroup\$