The abacus is still taught in Japanese schools, although not as intensively as it once was. But the centuries-old tool is still popular, and national tournaments attract elite competitors.
The caller read out the numbers at a speed evoking an auctioneer on fast-forward, each multidigit figure blurring into the next.
Within seconds, Daiki Kamino's right arm shot up in the air, triumphant. Not only had he heard every number, but he also had tabulated them and arrived at the correct, 16-digit sum: 8,186,699,633,530,061.
He did it all on an abacus.
For this bit of mathematical virtuosity, Daiki, 16, a high school student from Hiroshima, Japan, was crowned champion in the dictation event at an annual tournament in Kyoto, where competitors pull off dazzling arithmetic feats simply by sliding tiny beads along rods set within modest wood frames.
Daikiis rangy and slightly awkward in that teenage boy kind of way. He loves Japanese comics known as manga, along with fantasy role-playing video games. But for the last eight years, he has spent up to three hours a day practicing on the abacus, or "soroban" in Japanese.
"There are times when I'm not in the mood," he said. "But I start enjoying it once I start getting the right answers.
"I listen and move my fingers and repeat the numbers in my head," he added, trying to explain how he could possibly do what he does. "As soon as I hear the unit like trillion or billion, I start to move my fingers."
About 43,000 students take advanced soroban lessons at private schools in Japan, according to government estimates, although soroban associations say the number is higher. Many practitioners sit for exams to attain advanced qualifications known as kyu or dan, which are akin to belts in martial arts. Those who excel compete in national tournaments.
Showing the discipline of elite athletes, more than 800 contestants from across Japan, and a few from South Korea, gathered in an auditorium in Kyoto earlier this month to put their skills to the test.
The youngest competitor was 8, the oldest 69. Multiplying and dividing numbers with as many as 16 digits, they sent rapid clickety-clacks rippling across the room like a summer downpour.
For some events, the contestants dispensed with the physical soroban and mentally pictured the beads as they completed long pages of calculations.
One winner, a 20-year-old college student, broke his own Guinness World Record by adding in his head 15 three-digit numbers that flashed on a large screen at the front of the auditorium — all in 1.64 seconds.
Until the early 1970s, elementary school children across Japan were taught proficiency on the soroban, which was adapted from versions brought from China in the 15th century. It was once a common tool among shop owners, bank tellers and company accountants, and proved resilient well after electronic calculators were introduced.
Some older shopkeepers who learned to use the soroban as children still rely on them. At Daigen, a sushi restaurant in Kyoto, Yuriko Kawahara, 69, added up the cost of several meals on an old wooden abacus. "It keeps her from going senile," joked her husband and sushi chef, Tsumoru Kawahara, 69.
In the late 1970s, education officials, eager to bolster the population's scientific and technological skills, significantly cut back on soroban instruction.
Today, textbooks mandated by the education ministry include only a couple of pages on the soroban. Students receive basic lessons for just two hours a year in third and fourth grade.
But advocates for soroban instruction are pushing the ministry to introduce the old-school devices earlier.
"For little kids it's so easy to visualise numbers on the soroban," said Yasuo Okahisa, deputy director of the League for Soroban Education in Japan, host of the Kyoto tournament.
"Unlike the computer or calculator, you have to watch the movement of the beads with your eyes, and then think with your brain and make a move with your fingers," said Okahisa, as he slid the beads on an oversize abacus in the league's office in Kyoto. "It's a very foundational learning process."
The soroban is made up of columns of beads, with each column standing for a place value like ones, hundreds, thousands and so on. One bead on the top of each column is worth five, while four on the bottom of each column are worth one each. Students add, subtract, multiply and divide by sliding the beads up and down.
Some educators say the main reason for teaching soroban is to preserve traditional Japanese culture.
But Yukako Kawaguchi, 44, who runs one of the approximately 6,500 private soroban schools nationwide with her husband, Yoshiharu Kawaguchi, 47, said those who study the soroban intensively develop a sense of achievement.
"They will be viewed as a smart kid in class, and that will give them confidence," said Yukako Kawaguchi, a two-time national soroban champion who won her first competition when she was 14.
She admitted, though, that her soroban prowess did not help much in higher-level math like calculus. Today, aside from teaching, she mainly uses her mental soroban skills to add up grocery bills before she gets to the cashier.
On a recent afternoon during the first week of summer vacation for Japanese schoolchildren, about 30 students showed up at the school in east Tokyo.
A group of 5- to 9-year-olds crammed into a compact room, pinching beads between their thumbs and index fingers, their heads bent over worksheets filled with calculations of escalating difficulty.
Yukako Kawaguchi sat at a small desk at the front of the room. Students lined up in front of her for help.
Upstairs, Yoshiharu Kawaguchi worked with the school's most advanced students, two elementary-age girls who were preparing for the Kyoto competition.
For 2 1/2 hours, he set them on timed drills. Their foreheads damp with sweat, they ran through long pages of multiplication and division, adding columns of figures and finding the square and cube roots of numbers with decimals out to the trillionth place, clicking their soroban beads at astonishing speeds.
Niko Shibayama, 11, who has been studying soroban since kindergarten, used both her thumbs to click the beads, rat-a-tat. When she put the abacus aside to work on mental math, she swirled her pencil in the air and bobbed her head as if she were listening to music.
"It's fun," said Niko, who spends two afternoons and all morning Saturday at the Kawaguchis' school. "I am pretty competitive. So I never want to lose to anyone else." On long car rides, she likes to add up license plate numbers in her head.
At the Kyoto competition, Niko was committed but calm. During the dictation events, she tried to keep up with the caller but quickly lost track. "I could not even understand what they were saying," she said. "It all just sounded like 'wah wah wah wah wah.' "
After the tournament, Niko and two classmates from soroban school paged through the competition program. Niko put a check mark by the name of a 10-year-old who had been a finalist in the dictation event, a girl with ribbons in her hair and lace cuffed socks whose feet did not even touch the floor at the table where she sat.
"I want to know what was going on in her head!" Niko said.
She said she planned to return next year. When she gets older, Niko said she thought it would be fun to become a judge for the Guinness Book of World Records.
Her mother, Rutsuko Shibayama, 44, thought Niko's ease with competition might help her take strenuous school entrance exams in stride. But she was more happy her daughter had found an extracurricular activity she loved.
"I learned through Niko that the more you like something, the better you will get," Rutsuko Shibayama said. "I am really grateful that she found something that she's passionate about."
Written by: Motoko Rich
Photographs by: Chang W. Lee
© 2019 THE NEW YORK TIMES