which type? Is the 72 hour visa ok for the return flight.

Hi, I am traveling from Sydney to Beijing capital transiting in Nanjing for an hour along the way. We are staying in Beijing for 81 hours so require some sort of visa before flying to new york transiting through shanghai. We will return back to Sydney from new york with a transit in shanghai again. Can you please advise what type is required. Is it just the L tourist L for the stay in Beijing. Or do we require a multi entry? The other stops are only to transit we will not be leaving the airport. Thank you