Which room in the White House does the president sleep in?

Which room in the White House does the president sleep in?
There is a designated "Master Bedroom" in the residential part of the White House on the second floor; however, there are roughly ten more bedrooms in the second and third floors of the White House (the private residential area of the First Family), on top of the fact that the President is entitled to use any room in the White House for any purpose that he would like; he could literally set up a bed in the Oval Office and declare that his bedroom (some Presidents have used an office in the Old Executive Office Building across the street, after all).

With that in mind it is near impossible to answer your question with any degree of certainty, but it is most likely that the Obamas use the Master Bedroom as many Presidents have before them.