We will be arriving into Shanghai (from Chicago) staying less than 24 hours

before starting our cruise. Our cruise lasts 5 days and takes us to both Japan and Korea. We then return to Shanghai and then fly back to the US 1.5 days later. Can we use a visa exemption both before and after the cruise? Do we request the 72 hour exemption in the beginning and another 72 hour exemption after the cruise?