Need to enter China 3 times

Hi, I arrive in China from the UK and will stay one night. The next day I travel to Mongolia by Train.

After Mongolia I will come back to China for 2 weeks and then exit to go to North Korea. After North Korea I will come back to China agin for approx 4 weeks.

As I need to enter China 3 times, what is the best way to do this? 1 x transit visa and 1 x double entry visa? Or can I get a triple entry visa?

Many thanks