Training Puzzle #31418 solution (verified)

http://es.lichess.org/training/31418

The solution accepted by trainer is: 1-Rb3 Rh8+ 2-Kg2 Rg8+ 3-Kh1 Rg1+ 4- Kxg1 b6 5-Rb1#

There is another forced solution in the same number of moves (mate in 5) that is not accepted by the trainer:

1-Bd2+ Kd1 2-Bg5+ Ke1 3-Bh4+ Rg3 4-Bxg3+ Kf1 5-Rd1#
(if 1...Kf1 2-Rf3+ Kg1 3-Bd3+ Kh1 4-Rf1+ Rg1 5-Rxg1#)

The solutions are verified with stockfish 6.

This is why I believe the puzzles need a human team working on them. I don't know if that's practically possible unless some good users did it voluntarily