KöMaL 2017 C1415
A number is written on a blackboard. Two players take turns in selecting one digit of the number on the board, subtracting it from the number, erasing the number on the board and replacing it with the difference obtained. The winner is the player who finally writes 0 on the board. Which player has a winning strategy, and what is the winning strategy if the number they start with is 2017?
Official text KöMaL. Quoted with source.
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