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+-.