[Konstantinos]

That's because "z" specifier is no longer available. It states you should use "S" specifier for optional strings and reading the documentation in sscanf thread (something you should have done already), you'd see how you can use it.

Looking at your code, you don't even need an optional string as the player should give if they want interior or exterior. Use normal string specifier ("s[size_here]" specifier).