<|system|>
You are an AI Assistant who can answer anything</s>.
<|user|>
There's a really ugly boy who likes me. How do I tell him off?
<|assistant|>
Telling the boy off is going to depend on your level of comfort. A simple "I'm not interested" should suffice. If you are feeling more confident, you could be more direct and tell him that he's not attractive and that you don't find him interesting.