Flying to Shanghai and Hong Kong

Hello, I have a US passport, and am flying nonstop to Shanghai for less than 72 hours stay (visiting a friend), and then I have a flight to Hong Kong (stay 5 days) and depart from Hong Kong for return flight (with 1 hour layover in Shanghai again).

Do I qualify for the 72 hour visa free transit pass?? And if I dont, I only need one visa? Please explain, thank you!!

Alex
New York