Six girls on a couch: Why this picture is blowing people's minds?

Twitter can't seem to wrap its head around this picture of six girls sitting pretty on a couch.

Remember that dress? White-gold or blue-black -- It's been two years since that debate took social media by storm. Now there's another pic that's leaving people divided, and it's not a dress this time.
This photograph, shared on Reddit by user jr0d7771, has garnered hundreds of comments in just three days. The caption reads, "Find the middle girls legs" -- and that's exactly what everyone is baffled about.
At first glance you would say there are six girls, all smiles, sitting on a couch. If you look close enough at their legs, there are just five pairs. So who is hiding her legs?
One person wrote:

"The girl third from left is sitting on her own legs / feet. Note that her back isn't on the back of the sofa. Her right shoulder is in front of girl 2 and her left shoulder is even with or a little behind girl 4 to show that she is sitting on an angle. She is leaning back on girl 2. If you look at their legs, the shoes that are visible, and their jeans, you can see that there are five pairs of legs and each girl has a set of legs except for girl 3. (I initially thought that girl 3's leg was under girl 2's leg but it's not.) Girl 1 has her arms crossed and is holding a beer. Girl 2 is using both of her hands to hold her glass though with a quick glance it almost looks like girl 1 has three hands. If you look closely you can actually see the fingernails on the right hand of girl 2."

Another person commented, "She was photochopped."
Finally some clarity in doubt, thanks to Reddit user 'justonewordforyou' whose pictorial explanation drilled some sense.

So as you can see the second girl's legs are behind the first one's legs.
Still confused? Feel free to spend hours wrangling over the correct answer.
nilanjana@khaleejtimes.com