Magic number guessing method

In fact, this question is very simple. Let me tell you something. First, the magician asks the audience to write words on the paper, and then the magician will definitely ask the writer to show the words written on the paper to the audience. The magician can't see it. The question arises. Does he really have any special functions? No! The magician actually has an inside story, and this person is aware of it in the audience. Then when the author shows him what he has written, he will send a message to the magician by gesture. At this time, the audience are looking at the paper and won't pay attention. So the magician can easily know what is written on the paper. . I hope these answers can help you