1.Sc2? zz.

1...Kc4 2.Qc3+ Kd5 3.Qd4# 2...Kb5 3.Qc6+ Ka5 4.b4# (mm)

but 1...K*c2!

1.Sf3? zz but 1...Kc4!

1.Sc6? zz. but 1...Kc2!

1.Sb3! zugzwang.

1...Kc2 2.Qc3+ Kb1 3.Sd2+ Ka2 4.Qa3# 3...Ka1 4.Qa3# (mm)

[ 2...Kd1 3.Qd2# ]

1...Kc4 2.Qc3+ Kb5 3.Kc7 zz. Ka6 4.Qa5# 3...Ka4 4.Qc4# (mm)

[ 2...Kd5 3.Qd4# ]