1.♘a8, ♚x♘
2.♚b6 +, ♚b8
3.♖b7+, ♚c8
4.♖a8++

1-0

Another variant would be:

1.♘a8, c1=Q
2.♖b7+, ♚c8
3.♘b6++

1-0

And the other variant would be:

1.♘a8, c1=Q
2.♖b7+, ♚x♘
3.♚b6 ++

1-0