This is a game for two people.
Start by placing 9 counters in three rows as shown in the
illustration. Players take turns removing any number of counters
provided they are all in the same row. The player who is forced to
pick up the last counter loses.
There is a sure way for the first player to win. If the first player
doesn’t make the correct move, the second player can win.
This is the classic game of Nim. It can be played with any number of
counters and any number of rows.