Here is a puzzle I was shown a few days ago, try to solve it:

That's pretty cool.

Black actually wins this position, but the line is 16 moves long.

Why can't you just take the rook?

2 moves checkmate so y

If you take rook it's stalemate.

That's the trick - figure out how to avoid the constant checks when the rook cannot be captured.

It's actually mate in 18:

Here is the longest line:

If 9. Rd1 then Kb7 where there are no more checks. Rxf2 is an interesting way to stall mate though - so it looks like it is mate in 17.

Maybe I should change the title to mate in 17 then?

Nice Puzzle.  Thanks shepi13.