Question 133
The wizard Magò has a deck of 52 cards, arranged in a pile, face down. Magò separates the small packet consisting of the seven cards at the top of the pile, turns it over, and puts it under the pile. Now all the cards are again in a pile, but not all of them are face down: the seven at the bottom are turned the other way. Magò repeats the previous operation until it happens again that all the cards are face down. In total, how many packets of seven cards has Magò turned over?