Interesting Position

[Andrew McHarg]

I was playing a game earlier today and this position came up with black to play (bottom left square is a1). On initial glance it looked like it should be a draw. But it's actually a win by force for black. 8)

[pos]8/6Kp/7P/3k4/8/5n2/8/8 b - - 0 59[/pos]