A normal play game starting with 13 coins is a win for the first player provided he does start with a subtraction of 1: player 1: 13 - 1*1 = 12 Player 2 now has three choices: subtract 1, 4 or 9.
Now player 2 has to subtract 1, and player 1 subsequently does the same: player 2: 2 - 1*1 = 1 player 1: 1 - 1*1 = 0 player 2 loses .