There is a big round cake with 7 candles along the cake’s edges.

You need to blow out all of the 7 candles, which are placed in a circle.

The rule is:

once you blow out one candle, the candles near it will also be extinguished.

If you blow on an extinguished candle, it will reignite.

So if you blow on a candle, it will go from lit to unlit, and vice versa (as well as the candles on either side).

How can you extinguish all of the candles with the fewest blows?

Hint: Blowing on the same candle twice is the same as not blowing on it at all. Blowing on the same candle 3 times is the same as blowing on it once.