I just saw this fantastic endgame in ChessToday.net (#3719). This was an actual game between 2 Brazilian players (Marques and Pereira).
It is Black to move and win!! Can you find it the right continuation? No computer analysis please.
8/2k2p2/5p1P/2p1P3/2P5/nN4p1/p3K3/8 b - - 0 1
