1.f8=N+ (1.f8=Q {?} 1...Rf1+ 2.Kxf1 b1=Q+ {-+}) 1...Kg5

2.Rxd5+ Kf4 (2...Kh43.Ng6+ Kh3 4.Rh5+ {-+})

3.Ng6+ Kxe4 (3...Kg4 4.Nf6+ {-+})

4.Nf6+ Kd3

5.Ne5+Kd2

6.Ne4+ (6.Nc4+ Kd3 7.Ne5+ Kd2 {loss time}) 6...Kd1

7.Nc4 {!} (7.Nxc3+ Kd28.Ne4+ Kd1 9.Nc3+ Kd2 {pos.draw=}) 7...b1=N (7...b1=Q 8.Rxd4+ {-+}) (7...Rb1

8.Nxc3+ Kc1 9.Ke2 {+-})

8.Rxd4+ Nd2 (8...Nxd4 9.Ne3#)

9.Nxc3+ Bxc3

10.Rxd2 Bxd2.

11.Nb2# *

b)

1.f8=N+ Kg5

2.Ne6+ Kh5

3.Rh7+ Kg6

4.Rg7+ (4.Nf8+ Kg5 5.Ne6+ Kg6 {loss time})

4...Kh5

5.Nf6+ Kh6 (5...Kh4 6.Rh7#)

6.Ng4+ Kh5

7..Nf4+ Kh4

8.Nh2  {!} 8...Rf1+ (8...Ne3 9.Nf3#)

9.Nxf1 b1=Q

10.Ng2+ Kh5

11.Ng3+ Kh6

12.Nf5+ Kh5

13.Nf4# *