Can you figure out how many girls are in this photo? We're stumped!

Internet users are losing their minds trying to figure out just how many girls are in a mind-bending photo recently posted on Instagram.

The photo, taken by Swiss photographer Tiziana Vergari, was uploaded as part of a hashtag project called #WHPidentity, which features images celebrating individuality.

The girls, who are sitting in a plain room in Conthey, Switzerland, have lots of users puzzled — they can't quite figure out how many girls are in this photo.

Same but different | My entry #whpidentity for @instagram [thank you #instagram for this featuring ❤️]

A post shared by tiziana vergari iPhoneography (@tizzia) on

There are a few things we do know: There are at least two girls — one of them is tagged — and they're all wearing the same dress.

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The most popular guesses are two, three, four and 13 — but what do you think the number is?