How many times can you see the number 3 on this iPhone screen?
This may well frustrate you.
This picture of a doctored iPhone screen, asking people to count how many times to the number 3 appears, has been driving people round the bend.
We originally counted 18, and we were wrong. How many can you get?
Look at the entire screen.
This first appeared on Facebook in February, and has received more than 145,000 comments – and it has since been doing the rounds on social media.
Incidentally, it refers to the numeral '3' alone, so don't go counting the number of dots on the signal or the WiFi bar.
The right answer is, of course... 19.