To tell the king's fortune.

What is the surname of others calculated by the fortune teller?

This fortune teller has two props, one is a cloth spread on the ground, on which are squares filled with surnames. The second prop is a dozen cards like a deck of playing cards, and each card is also full of surnames. First of all, when you go to fortune-telling, the fortune-teller will ask you to find out your surname on many cards (only one card has your surname on it), and then the fortune-teller will ask you to put the cards in a grid with your surname on the cloth (there are more than a dozen surnames on the cards and a grid on the cloth). After that, the fortune teller will give you a finger and tell you your last name. You will be surprised.

It's actually quite simple. The surnames on the card and the surnames on the grid are arranged regularly. Only a dozen surnames on the card are duplicated with those on the grid, and the duplicated surnames are your surnames. This arrangement is called matrix arrangement.

On the surface, fortune telling is actually a game of number arrangement. A fortune teller can make you earn dozens to hundreds by playing a game with you.

It took me nearly two hours to understand such a simple number game. Pity my IQ.