Begging to crack: Take a deck of cards and let me randomly draw one and put it in. You can guess which one it is after washing it a few times.

1. These cards are specially made. Playing cards are square, with two long sides and two short sides. There is a special card. Its two short sides are not the same length, so the card becomes trapezoidal instead of rectangular. Of course, the difference is very small, and it is hard to see. The card you drew was reversed when you put it back, so only this one is not in line with the other 53 cards. At this time, I touched it and felt it.

2. After drawing cards, you remember one of the remaining 53 cards. When someone puts the card back, you ask him to put it above (or below) the card you just remembered, and then shuffle the cards. There is little chance that the next two cards will be washed away. At this time, spread out the cards. You just need to find the card you just remembered, and you can find the card that was drawn and put back by others on it or below it. (Of course, the whole process should be natural, relaxed and not seen by others. You deliberately let him put the card next to the card you remember. )

Hehe, I hope it helps.