Excuse me, street fortune teller, how to do it? "You don't have to ask, you know your last name."

First, arrange all surnames into a square. For example, if there are a hundred, they will be arranged in ten rows, with ten in each row.

Then copy each line of words on a card and give each card a singular name. ( 1,3,5,7。 . . . . . )

Then copy the words in each column on a card and name each card with an even number. (2,4,6,8。 . . . . )

At this point, he has 20 cards in his hand, and only one surname is repeated in any odd card and any even card combination. At this point, the props are complete.

Then, recite the square (usually a hundred surnames).

Set up a stall I'll show you the odd card first, so that you can find the one with your last name. (Tell him the line in the box). I'll show you the even card and let you find the last name. (equivalent to telling him which word the column in the square matrix is). Then pretend to measure your fingers. There will be enough time to solve this problem.

I hope the above answer didn't ruin anyone's job.

I hope the landlord will give me extra points for answering such a sensitive question.