A Japanese mental health counsellor has broken the world record for reciting pi, the ratio of the circumference of a circle to its diameter, from memory.
The symbol used for pi is a letter from the Greek alphabet
Akira Haraguchi, 59, managed to recite the number's first 83,431 decimal places, almost doubling the previous record held by another Japanese.
He had to stop three hours into his recital after losing his place, and had to start from the beginning.
Pi is an infinite decimal whose numbers never repeat in a pattern.
Mr Haraguchi, from Chiba, east of Tokyo, took several hours reciting the numbers, finishing in the early hours of Saturday.
"I thank you all for your support," he told reporters and onlookers at the public hall in Tokyo.
He hopes to be listed in the Guinness Book of World Records to replace his fellow countryman Hiroyuki Goto, who managed to recite 42,195 numbers as a 21-year-old student in 1995.
Mr Haraguchi had already recited the ratio up to about 54,000 digits last September, but was forced to drop the challenge when the facility hosting the event closed for the night.
So far, pi has been calculated to 1.24 trillion decimal places with the aid of a supercomputer.
Conventionally, 3.14159 is used as pi.
Pi is known for turning up in all sorts of scientific equations, including those describing the DNA double helix, a rainbow, ripples spreading from where a raindrop fell into water, waves, navigation and more.