The man on the top floor
A man lives in an apartment on the top floor of a building, on the 20th floor.
Every morning he takes the elevator down to the ground floor and leaves the building to go to work.
Upon his return from work he takes the lift to the 6th floor and has to walk the rest of the way up a staircase to where he lives on the 20th floor.
However, when it rains, he takes the lift right up to the 20th floor.
How can this be true?