Puzzle of the week #300

Submitted by Eugen on Mon, 07/18/2016 - 22:06
Mate in 4
Chess Diagram
[Event "Puzzle #300"][Date "2016.07.18"][Result "1-0"][SetUp "1"][FEN "7N/3K1Npk/6p1/8/8/1B6/8/8 w - - 0 1"]
This puzzle covers the summer of 2016 before we start our level 5 group in September. The task is very simple:
a) White to checkmate in 4; no computer help please!
No points are available for this puzzle; however I will review any answers I get. Its purpose is to give our current and future students an idea what to expect starting September. The answers will be published next time together with puzzle #301.

Puzzle #299 solution:
Game Sladjan_Dimitrijevic (Serbia) - Valer Eugen Demian (Canada), chess.com 2015
a) The six principles of the Lucena position
Yes, they do apply:
1. The strong King must support the pawn, while the weak King must block it
2. The strong Rook must be very aggressive supporting the pawn advance: its best position is behind the pawn, followed by lateral and last in front of the pawn
5. The weak Rook must attack the strong King from as far away as possible
6. The weak King should cover the shorter side (less files between the passer and a board side)
No, they don't apply:
3. The strong Rook must also cut the weak King as far away from the pawn as possible
4. The weak Rook cannot deliver perpetual check from afar unless its own King either helps it or blocks the pawn

b) Yes, black can win
c) The game winning line was:
[Event "Puzzle #299"][Date "2016.06.12"][Result "0-1"][SetUp "1"][FEN "3R4/8/8/7r/8/2K5/3p4/3k4 b - - 0 83"]83... Rc5+ 84.Kb2 Rc2+ 85.Kb1 Rc1+ 86.Kb2 Ke2 87.Re8+ Kf3 88.Rf8+ Ke4 89.Re8+ Kf5 90.Rf8+ Ke6 91.Re8+ Kf7 92.Rd8 d1=Q 93.Rxd1 Rxd1 94.Kc2 Rd8

Correct solutions:
Aaron Y, Deryk - 14 points
Yakov, Jalen - 12 points
Benjamin, Cody - 9 points
Daniel, Bradley - 7 points
Coco - 4 points
Aaron W - 3 points

Bradley - 195 points
Jalen - 191 points
Coco - 149 points

Benjamin - 138 points
Daniel - 135 points
Cody - 134 points
Deryk - 131 points
Aaron W - 82 points
Yakov - 74 points
Ethan - 73 points
Aaron Y - 58 points
Shya - 10 points
Dheera - 5 points