Jack is taking a tour through a museum's American Presidents exhibit. The person leading the tour tells him "We have a picture of each presidency. Currently Barack Obama is the 43rd person to hold the office." But Jack quickly realizes that there are 44 pictures on the wall. But while walking through the exhibit he realizes why this is. Why is there one too many photos?
One president served non-consecutive terms (there was a president between his terms) so he held two different presidencies. The president who really did this was Grover Cleveland.