I'm at the moment in China holding a F visa (single entry). Before I'm going back to Europe I would like to visit Hong Kong for a few days. I would fly from Shanghai to Hong Kong and from Hong Kong back to Shanghai where I have my flight back to Switzerland. Do I need to apply for another chinese visa (transit or something like this) I would not leave the airport in Shanghai, I would just wait for the connection flight? Could there be a problem in Hong Kong that they don't let me board the plane because I have no visa for China?

Thanks for your help