http://fr.lichess.org/training/22354
Nf6 accepted, Rg7 refused, despite it mates on 5 too (1.Rg7 Kh8 (Kf8 2.Rf1 Ke8 3.Re7 Kd8 4.Rf8) 2.Rd7 Kg8 (Qxc3 3.Nxc3 Kg8 4.Rb1 Kf8 5.Rb8)3.Rd8 Kf7 4.Rf1+ Ke6 5.Rf6)
Nf6 accepted, Rg7 refused, despite it mates on 5 too (1.Rg7 Kh8 (Kf8 2.Rf1 Ke8 3.Re7 Kd8 4.Rf8) 2.Rd7 Kg8 (Qxc3 3.Nxc3 Kg8 4.Rb1 Kf8 5.Rb8)3.Rd8 Kf7 4.Rf1+ Ke6 5.Rf6)