Hi there, I'm going to be in Shanghai, flying from Singapore to Shanghai on January 2, then leaving on January 4th. I have read about not needing a visa since I am a US Citizen if I am there for 48 hours. However, because of my flights, I will be in Shanghai for 50 hours. Will I need a visa, or will my being at the airport within the 48 hour time period be good enough so I will not need to get a visa?

Thank you!