On his way to work each morning, a man living on the fifteenth storey of an apartment building takes the elevator to the first floor.
In the evening, he gets into the elevator, and, if there is someone else in it he goes back to her floor directly.
Otherwise, he takes the elevator from the first floor to the seventh floor and then walks to the remaining eight floors. However, he doesn’t need the exercise and doesn’t particularly like walking up the stairs.
So why does he do this?