Mate in 18

1.c8Q Qxc8 Try: 1...Nf5?+ 2.Qxf5 Qh8+ 3.Kd3 Qxc3+ 4.Kxc3 Ra6 5.d7! g1N 6.Qc2+ Kb5 7.Qd3+ Ka4 8.d8Q Nxe2+ 9.Kc2 Bg6 10.Qxg6 Nd4+ (10...a1N+ 11.Kb1 Nc3+ 12.Bxc3 Ne6 13.Qge8+ b5 14.Qd5 Nc5 15.Qa2#) 11.Qxd4 a1N+ 12.Kb1 Rxg6 13.b5+ Kxb5 14.Qb4+ Ka6 15.Qa5# 2.Nxc8 with A) 2...Ra6 3.Nb6+ Rxb6 4.Qa3+ Kb5 5.Qa5+ Kc6 6.Qc5+ Kd7 7.Qc7+ Ke6 8.Qe7+ Kf5 9.Qxg5+ Ke6 10.Qe5+ Kd7 11.Qe7+ Kc6 12.Qc7+ Kb5 13.Qc5+ Ka4 14.Qa5+ Kb3 15.Qa3+ Kc2 16.Qc3+ Not 16.Qd3+? Kd1 17.Bxe3+ Ke1 18.Qd2+ Kf1 19.Qd1# 16...Kd1 17.Qc1+ Kxe2 18.Qe1# MATE (1) B) 2….Nf5+ 3.Kd3 Ra6 4.b3+ Bxb3 5.b5 Kxb5 6.Qxb3+ Kc6 7.Qc4+! Kd7 8.Qb5+(1) Kd8 9.Qxf5 Rxd6+ Try: 9...Ra3?+ 10.Kc4 Ra4+ 11.Bb4 (11.Kb5 Ke8 12.Qg6+ Kd8 13.Qf6+ Kxc8 14.Qf8+ Kd7 15.Qe7+ Kc8 16.Qc7#) 11...Rxb4+ 12.Kxb4 a1Q 13.Qf8+ Kd7 14.Qe7+ Kc6 15.Qc7+ Kd5 16.Qc4# 10.Nxd6 a1Q 11.Qc8+ Ke7 12.Nf5+ Kf7 13.Qd7+ Kg8 13...Kf8 14.Qe7+ Kg8 15.Nh6+ Kh8 16.Qf8+ Kh7 17.Qg8+ Kxh6 18.fxg5# MATE (2) 14.Nh6+ Kh8 15.Qd8+ Kg7 16.Qxg5+ Kh7 16...Kf8 17.Bb4+ Ke8 18.Qe7# MATE (3) 17.Qg8+ Kxh6 18.f5# MATE (4) Sequence that culminating in matte in 18 moves, but no univocal In (1) 8...Rc6 9.Qxb7+ Ke6 10.d7 Rd6+ (10...Rc7 11.Qxc7 Nf7 e.g. 12.Qc4+ (12.Qc6+ N5d6 13.f5+ Kf6 14.d8Q+ Nxd8 15.Qxd6+ Ne6 16.Qxe6+ Kg7 17.Qg6+ Kh8 18.Bc3#) 12...Kxd7 13.Qxf7+ Kxc8 14.Ba5 Ne7 15.Qxe7 Kb8 16.Qc7+ Ka8 17.Bb6 a1Q 18.Qc8#) 11.Nxd6 Nf7 12.Nxf7 g1Q e.g. 13.d8N+ (13.Ng5+ Qxg5 14.fxg5 Nd6 15.d8N+ Kf5 16.Qd5+ Kg6 17.Qg8+ Kf5 18.Qe6#) 13...Kf6 14.Bc3+ Kg6 15.Nh8+ Kh6 16.Ndf7+ Kh7 17.Ng5+ Kh6 18.Qh7#;