27 sheets
Anything will do.
Let the audience recite one.
Then shuffle the cards
Divide into three layers
Show him each stack of cards in turn.
Ask him if he has your card.
Pile his cards in the middle.
Don't shuffle the cards
Continue licensing
Or a three-layer stack
Repeat the above process.
Then put his cards in the middle.
Redistribute cards
This time, his cards must be in the middle of the pile!
I wish the landlord a happy magic!