You have a 4×5 chess board as follows:
You can move the four bishops in any order (not necessarily alternating black and white), provided that no move puts a piece in danger of being captured by a bishop of the opposite color.
What is the fewest number of moves needed for the black and white bishops to exchange places?
You could take a mirror and put it up to the board. therefor it would take 1 move, or 0 moves!