I wrote a word myself, and the fortune teller can guess it.

One way is to give you some pieces of paper. You can point out which one has your last name on it and let him know what your last name is. As for guessing the full name, I don't know, and from a mathematical point of view, I can't guess it. The landlord may not have experienced it personally. Put some paper on you. It can't be just a show. I will definitely ask you questions, such as' Look at that paper with your last name on it'. If you answer, you can count your name. There are many similar games on the Internet, and there are also detailed mathematical principles. Actually, it is the concept of intersection in mathematics. In addition, there must be other actions before and after writing the name. In fact, your name has long been quilted. Third, it is also possible that there is something under the white paper, from which he can see what you wrote. Fourth, give you a pen that can't write, let you write your name on white paper, and see what you have written through scratches.