What exactly is Obama doing during this class photo at the G20 summit?

As per tradition, world leaders attending the Group of 20 economic summit in Hangzhou, China took a class photo. It seems as if President Obama’s mind was elsewhere during part the session. Check out the first of these two photos.

Pres Obama seemed distracted while waving during G-20 group photo. Earlier seen chatting with IMF's @Lagarde. pic.twitter.com/nrDu7cSdVH

— Mark Knoller (@markknoller) September 4, 2016

Wonder what was so distracting?