After thinking it over, one user finally cracked the solution: "Think I've got it, assuming I'm informed of the number of cards you flip... Divide into a pile of 99 and a pile of the rest.
One Redditor proposed: "Separate them into one pile of 99 and another of the rest, and then flip the pile of 99."
The puzzle, which was shared on Reddit, goes as follows: "You take a large pile of cards face down, flip 99 of them face up, and blindfold yourself.".
The puzzle then continues: "There will be exactly 99 face up to start, so at least one flip is necessary."
Someone else wrote: "If I am blindfolded, I would think they are all face down because you said you 'secretly' flipped 99 of them face up.
