Puzzle of the Day 21 November 2016 |  Find the best move

1. ... f4 2. Kb4 Kg2 3. a5 f3 4. a6 f2 5. a7 f1=Q 6. a8=Q+ Qf3 7. Qa2+ Qf2 8. Qd5+ Qf3 9. Qd2+ Qf2 10. Qg5 Qd4+ 11. Kb5 Qd3+ 12. Kc6 Kf2 13. Rf8+ Ke2 14. Qe5+ Qe3