This figure is a challenge to intelligence. If you look at the image you can count fifteen young people in different positions. But ... what if we exchanged boxes A and B? Click on the image to check it.
The image is recomposed from its pieces, so that the young women apparently recombine again. But ... do not you find any missing ?. If the accounts do not fail you will see that now there are only 14 What happened to the missing one?
If you try to solve this apparent paradox by checking young for young and the parts of them that have been combined, you will only get into a dead end. Actually the trick is that a small part of each young person disappears so that in the resulting image one of them has been completely eliminated. Amazing, right?