If you don't count to 20, you must count to 19, because after counting to 19, there are still 20 left, and the opponent will definitely lose.

This becomes a competition for 19.

If you want to count to 19, be sure to count to 15 (please ask if you don't understand this step).

Be sure to count to 15, and be sure to count to 1 1.

……

Decreasing four numbers in turn.

That is to say, we must count to 7 and 3.

So if you want to win, you must count first, and you must count first.

Then, regardless of the number of opponents, you just count to 7 according to the strategy, 1 1, 15, 19.

You got it?

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