A baffling puzzle posted on Twitter has left the web stumped, as viewers struggle to determine the correct answer.
The brainteaser, which was shared on by Twitter user @Purp, shows a pot of coffee being poured into a sketch of different pipes, which collectively lead to four coffee mugs.
The puzzle asks users to figure out which of the coffee mugs the liquid will reach first - and it's harder than it first appears, according to the Daily Mail.
The user who uploaded it told her followers: "Let's see whose brain is working". It was quickly shared thousands of times as users argued over the right answer.
![Which cup will be filled first? Photo / Twitter, @Purp](https://www.nzherald.co.nz/resizer/v2/74POOCRLREMKRKSI2PCA7IPX64.jpg?auth=3906f2ce147cdc0da599ca0c229b4ec959c75ceeca0e701b665f9f0b1ad67aa8&width=16&height=16&quality=70&smart=true)