White has one more pawn. However, this is not enough because his king is cut off from the center. White should force bR to leave from the file 'b". After this the wK can "work". For this White must exchange the pawn "f".
1.f6! [Not successful promotion of a pawn "e": 1.e4? Kg5! (1...Kg4? 2.e5 Rb5 3.e6 Re5 4.Rf7+- ) 2.e5 Re7 3.e6 (3.f6 gxf6 4.exf6 Re6= ) 3...g6 4.Rf7 Re8 5.fxg6 Kxg6~~ ] 1...Kg5! [1...g5 2.e4 Kg4 3.Re8 Kh5 4.Re7 Rb8 5.e5 Rf8 6.Kb2+- ; 1...gxf6 2.Rxf6 Rc7 3.Kb2+- ] 2.fxg7 Rxg7 and now, the king must rush to the center carefully 3.Kb2 Re7 4.Kc3! [4.Kb3? Rxe3+= ; 4.Rf3? Kg4 5.Rf4+ Kg5 6.Rf3 (6.Rc4 Rxe3= ) 6...Kg4= ] 4...Rxe3+ 5.Kd4 Ra3! [5...Rh3 6.c4 Rh4+ 7.Kc5 Rh6 8.Kb6+- ] 6.c3! zz [Thematic try 6.c4? Ra5 zz WTM 7.Rc8 Kf6! (7...Kf5? 8.Rxc6+- ) 8.Rxc6+ Ke7= ] 6...Ra5 7.c4 zz BTM 7...Kg6 8.c5 [8.Rc8? Kf6 9.Rxc6+ Ke7= ] 8...Kg7 [8...Rb5 9.Rc8 Kf6 10.Rxc6+ Ke7 11.Rd6 similar of the main line] 9.Rc8 Kf7 10.Rxc6 Ke7 11.Rd6 Ra7 [11...Ra4+ 12.Kd5 Ra5 13.Kc6 similar of the main line] 12.Kd5 Ra5 13.Kc6 Ra6+ 14.Kc7+-.