What's wrong with the bird's mental calculation?

I haven't seen it before. I finally saw it yesterday. Careful observation, there is a secret, which is magic.

1。 Larks have been trained since childhood.

2。 As for how to know your name and birthday, think about it, and you will understand why you should choose a card before calculating, take a card with your birthday or name in your hand, and then cover the area with your birthday or name on the ground with this card. As long as you are careful, you will find that there is only one information overlap between the cards you choose and the information on the ground coverage area, that is, your own name or birthday. The stall owner only needs to remember which card corresponds to which area and use what name, and use relevant skills.

It is not easy to make money if you intend to publicly decrypt it.