One, two, three… wait, how many girls are there in this photo? That’s the question that’s been puzzling the Internet for a week with people lining up in groups according to how many girls they think are in the photo. Swiss photographer Tiziana Vergari posted the photo on Instagram as part of a weekend hashtag project about identity and it’s already received over 21,000 likes and 4,000 comments.

I myself have switched camps a few times. Every time I think I’ve figured out the optical illusion, I notice something new that leads me to doubt my answer. So how do commenters weigh in on this debate?

Their answers range from two to 13 and some people see twins, triplets or even quadruplets in the picture, which makes the total number of girls in the photo difficult to land on.