going to Shenzen from Hong Kong. Then fly from Hong Kong to Shanghai, single entry visa or double entry???

Once again, THANK YOU Mr John Nash for your prompt reply to my query. But I would like to be very clear regarding visa. I will be going to Shenzen from Hong Kong. Then fly from Hong Kong to Shanghai. Will I only need the single entry visa or double entry??? Form V2011A. Will I be able to print from computer??? Thank you kindly.