the puzzle is supposed to illustrate the fastest way to promotion

Thanks for posting these puzzles. If anyone wishes to further drill themselves on simple endgame puzzles such as these I recommend taking a look at Polgar's 5334 puzzle book which has a section of I think around 125 endgame puzzles of a simple nature such as these. Take care.

For those of you who arent familiar with that, this position is called a closed position because the pawns block each other. Usually if you sacrifice a piece you can break through

that one's not completely endgame though