Visiting both Beijing and Shanghai

Hi,
I have the following itinerary:

Day 1-3 Beijing from United States
Day 4-8 Cambodia/Vietnam
Day 9-11 Shanghai back to the United States

I see a rule that you cannot travel between the Beijing region and the Shanghai region on a 144 hour visa exemption. But since I am departing China and then coming back into China. So will I receive a new 144 hour visa exemption in Shanghai? Or am I limited to only visiting one of the cities/regions?