Correct answer: Ng61...f6 2.Bg6# 1.Ke5?? zz 1...f5 2.Bg6# but 1...f6+! 1.Kg5?? zz 1...f5 2.Bg6# but 1...f6+! 1.Kg4?? zz 1...f6 2.Bg6# but 1...f5+! 1.Ke4?
