Four Aces

You ask any viewer to call a number between 10 and 20 and stack one of them in a separate pile in the amount that the viewer called. Next, you count the sum of the digits of the named number, remove the number of cards from the top of the stack that is equal to this amount, and return them back, but put them on top of the deck. The top card is placed face down, and the remaining cards are put in place. Then again ask any spectator to call any number from 10 to 20 and do the same. In this way, you act 2 more times until you set 4 cards aside. After that, you open these 4 cards and they all turn out to be aces. The audience is very surprised.
The secret of the focus is that before starting the focus, the aces are placed on the ninth, tenth, eleventh and twelfth places from the top. Everything else happens automatically by itself.