OBVIOUSLY

Two men in a lift going up stops at the Seventh floor.
The doors open and a man makes to get in.
He looks first at one and then the other of the two men in the lift and says, 'You going down?'
'We're going up,' says one of the men in the lift.
The man stepping in steps back out of the lift and the doors close.
The man of the men in the lift hasn't spoken says, 'Obviously.'