Chapter 5: The Weight of Knowing
The middle schooler stared at Dojun like he had just spoken in ancient Sumerian.
“So x equals negative b, plus or minus the square root of b squared minus four a c, all divided by two a,” Dojun said, tapping the quadratic formula he had written on the notebook. “It works every time. You just plug in the numbers.”
“But why does it work?” His cousin Yuri—Uncle Sangchul’s daughter, fourteen, with braces and a permanent expression of mathematical betrayal—crossed her arms. “My teacher just says memorize it. But I can’t memorize things I don’t understand.”
Dojun paused. He had been about to say the same thing his professors had said to him: just memorize it, understanding comes later. But he was sixty-three years old inside, and he knew that understanding never came later if you didn’t plant the seed now.
“Okay,” he said. “Forget the formula. Let me show you where it comes from.”
He took the notebook and started from scratch. Not with the formula, but with a simple square. “If I tell you x squared equals nine, what’s x?”
“Three. Or negative three.”
“Right. Easy. Now what if I tell you x squared plus six x equals seven? Harder, right? But watch—” He drew the geometric completion, turning the algebraic expression into a visual shape. A square with a missing corner. “We’re trying to complete the square. Make it whole. And when you complete the square for any quadratic equation, the formula just… falls out. It’s not magic. It’s geometry.”
Yuri leaned forward, braces glinting. “Oh. Oh. That’s why it’s called completing the square?”
“That’s why.”
“Why didn’t my teacher just say that?”
“Because your teacher has forty students and twelve minutes per topic. She doesn’t have time to explain the why. That’s what I’m here for.”
They were sitting in Uncle Sangchul’s apartment in Mapo-gu, a modest three-bedroom that smelled of doenjang jjigae and the faint chemical sweetness of the hair salon that Sangchul’s wife operated from the living room on weekdays. It was Saturday afternoon, and Dojun had come straight from Namdaemun Market—his second consecutive weekend visit to his mother, who had greeted him with the same mixture of delight and suspicion.
“Two weekends in a row,” she had said, pressing a container of freshly made kimchi into his hands. “Are you sure you’re not in trouble?”
“I’m not in trouble, Mom.”
“Because if you’re in trouble, you can tell me. I know people.”
“You know banchan customers.”
“Banchan customers know everyone. Mrs. Choi’s son is a police officer. Mr. Hwang’s nephew is a lawyer. I have connections, Dojun-ah.”
He had laughed and hugged her—something he was still getting used to doing, this physical affection that his twenty-year-old self had been too stiff and embarrassed to offer and his sixty-three-year-old self had desperately wished for at the end. She had stiffened at first, surprised, then melted into it with a small sound that might have been a sigh or might have been a suppressed sob.
“Eat more,” she had said when he let go. “You’re too thin.”
“You say that every week.”
“And it’s true every week.”
Now, an hour later, he was teaching quadratic equations to a fourteen-year-old who was far smarter than her grades suggested, and discovering something unexpected: he was good at this. Not just at the math—the math was trivial—but at the teaching. At finding the exact analogy, the precise visual, the perfect simplification that made a concept click.
In his previous life, he had been a terrible teacher. At Prometheus Labs, his code reviews were legendary for their brutality—he would red-line entire functions with comments like “This is wrong in seven ways, all of them fundamental.” Junior developers cried. Senior developers avoided his pull requests. Hana had once told him that his feedback style was “technically accurate and emotionally devastating.”
He hadn’t understood why that was a problem. The code was wrong. He pointed out that it was wrong. What more was there to say?
Everything, it turned out. There was everything more to say. How to frame criticism as curiosity instead of condemnation. How to ask “What were you trying to achieve here?” instead of “Why did you do this?” How to make people feel smart for asking questions instead of stupid for not knowing answers.
It had taken him forty years and the loss of nearly every meaningful relationship to learn these things. But he had learned them. And now, sitting at a kitchen table with a fourteen-year-old and a quadratic formula, he was putting them to use.
“Okay, try this one,” he said, writing a new equation. “x squared minus five x plus six equals zero.”
Yuri picked up her pencil and started completing the square. Her handwriting was messy and her arithmetic was slow, but her logic was sound. After three minutes, she looked up.
“x equals two or x equals three?”
“Perfect.”
“I DID IT!” She slammed the pencil down with enough force to rattle the teacups. From the kitchen, Uncle Sangchul poked his head in.
“Everything okay? Sounds like someone’s being murdered.”
“I’m being educated, Appa. It’s different.”
Sangchul looked at Dojun with an expression of bewildered gratitude. “She’s been failing math for two semesters. What did you do?”
“I just explained the why, not just the how.”
“The school should try that sometime.” He retreated to the kitchen, shaking his head.
Yuri was already writing the next problem herself, testing variations. “What if the number under the square root is negative? Like, b squared minus four a c is less than zero?”
“Then there’s no real solution. The parabola doesn’t cross the x-axis.”
“But is there a not-real solution?”
Dojun smiled. “That’s a question for high school. But yes. They’re called imaginary numbers.”
“Imaginary? Like made-up?”
“Like… numbers that exist in a different dimension. They’re perfectly real in their own way. Mathematicians just gave them a terrible name.”
“Mathematicians give everything terrible names. ‘Completing the square’ sounds like a furniture assembly instruction.”
He laughed. This kid was going to be fine.
On the subway home, Dojun’s phone buzzed. A text from Hana:
Hey, the group project demo is looking great. Minjae’s data is solid. Your algorithm is clean. I think we might actually impress Dr. Yoon. Coffee tomorrow to prep?
He typed back: Can’t tomorrow. Coding contest is Monday. Spending the weekend preparing.
The SNU coding contest? You’re competing?
Yes.
I didn’t know you were into competitive programming.
I’m not, really. But the prize money would help.
A pause. Then: Five hundred thousand won, right? That’s a lot of ramyeon.
I’m trying to eat less ramyeon. My mother’s orders.
Your mother sounds smart. Good luck on Monday. Destroy them.
I’ll try to be moderately competitive.
No. Destroy them. Design students are vicious and we respect nothing less than total victory.
He stared at the phone, grinning. Hana in 2006 texted the way she talked—direct, warm, slightly aggressive. In his previous life, her texts had evolved over the years into something more guarded, more professional, until the last one she ever sent him was a single line: I left the company keys on your desk.
Not this time, he thought. This time, the texts stay warm.
Sunday. One day before the contest.
Dojun sat in the SNU computer lab, the only person there at 7 AM on a weekend. The lab was in the engineering building’s third floor, a room of twenty workstations arranged in rows, each equipped with a CRT monitor that hummed faintly and a keyboard yellowed with age. The room smelled of dust and old electronics—the particular institutional smell of every university computer lab in the world.
He had been here since six, working through contest preparation with a methodical intensity that would have looked, to any observer, like the focused study of a hardworking student.
In reality, it was something stranger: a dress rehearsal in self-limitation.
The contest format was five problems in three hours. He had pulled previous years’ problem sets from the contest archive and was solving them—not as fast as he could, but at the speed a talented sophomore should solve them.
Problem A: Array manipulation. True solve time: ninety seconds. Performed solve time: twelve minutes.
Problem B: Graph shortest path. True solve time: two minutes. Performed solve time: twenty minutes.
Problem C: Dynamic programming with memoization. True solve time: three minutes. Performed solve time: thirty-five minutes.
Problem D: Combinatorial optimization. True solve time: four minutes. Performed solve time: forty-five minutes.
Problem E: Advanced graph theory with network flow. True solve time: eight minutes. Performed solve time: he wouldn’t solve this one at all. A sophomore who solved all five problems, including a problem that typically stumped graduate students, would raise red flags.
The plan was to solve four of five problems in approximately two hours and twelve minutes. Fast enough to win or place near the top. Slow enough to be remarkable but not impossible.
The variable he couldn’t control was Seokho.
He had looked up Jang Seokho’s competitive programming record. It was formidable. Two-time Korean champion. Top fifty in the ACM-ICPC Asia regionals. Consistent solver of five-out-of-five in national contests with time to spare.
If Seokho solved all five, Dojun would finish second—which was fine. Second place still won three hundred thousand won and credibility. But there was a part of him, the competitive core that had driven him to build a hundred-billion-dollar company, that bristled at the idea of deliberately losing to anyone.
You’re not here to win a coding contest, he told himself. You’re here to build a life. The contest is a stepping stone, not a destination.
But his fingers wanted to solve Problem E. They itched for it. The network flow algorithm was elegant—Dinic’s algorithm with capacity scaling, a solution he had implemented dozens of times in production systems—and leaving it unsolved felt like leaving a sentence unfinished.
Discipline, he thought. The hardest skill isn’t solving problems. It’s knowing which problems not to solve.
He closed the practice set and leaned back. The CRT monitor cast a faint blue glow on his face. Through the lab window, he could see the campus coming to life—a few early-morning joggers, a maintenance worker sweeping the path, the first cherry blossom buds beginning to swell on the trees lining the main walk.
Spring was coming. The world was waking up.
At noon, Dojun left the lab and walked to the campus cafeteria. He bought a tray of bibimbap—the university’s version, heavy on the rice, light on everything else—and sat at a corner table.
The cafeteria was filling up with the weekend study crowd: students in sweats and glasses, hunched over textbooks, fueling marathon sessions with cheap coffee and cheaper food. Dojun ate and observed, cataloging the differences between 2006 and the future he remembered.
No laptops on the tables. A few students had chunky ThinkPads in their bags, but nobody worked on them in the cafeteria—WiFi didn’t reach here, and the idea of a “coffee shop workspace” hadn’t yet become a cultural norm. People came to the cafeteria to eat, not to perform productivity.
No earbuds. Students who wanted music had MP3 players—iRiver, mostly, the Korean alternative to the iPod—with wired headphones. The iPod existed but was expensive and rare in Korea.
No constant checking of phones. Flip phones sat face-down on tables or in pockets. They were tools for calls and texts, not portals to an infinite stream of content. When people talked, they talked to each other. When they were alone, they were actually alone.
We gave up so much, Dojun thought, for the convenience of having everything in our pockets. We just didn’t know we were giving it up until it was gone.
He was halfway through his bibimbap when a shadow fell across his table.
“Park Dojun?”
He looked up. A young man stood there, tray in hand, with the coiled energy of a compressed spring. Medium height, lean build, sharp features arranged in an expression of polite curiosity that didn’t quite mask the competitive assessment underneath. He was wearing a KAIST hoodie—navy blue, with the university’s logo in white—and carried himself with the particular confidence of someone who was used to being the smartest person in any room he entered.
Dojun’s chopsticks froze over his bibimbap.
“I’m Jang Seokho,” the young man said. “KAIST. I saw your name on the contest registration list. Mind if I sit?”
In forty years of memories, Dojun had a thousand images of Jang Seokho. Seokho at thirty, presenting a keynote at CES with the controlled charisma of a man who knew his product would reshape an industry. Seokho at forty, sitting across a negotiation table, eyes cold, dismantling a merger proposal clause by clause. Seokho at fifty, unexpectedly calling Dojun on a Friday night to ask if he wanted to get a drink, and the two of them sitting in a quiet bar in Itaewon, not talking about business for the first time in twenty years.
But this Seokho—twenty-one, KAIST junior, with acne scars on his jaw and chalk dust on his hoodie sleeve—was someone Dojun had never met.
“Sure,” Dojun said. “Have a seat.”
Seokho sat across from him and arranged his tray with the precise efficiency of someone who organized everything, including meals. Rice on the left, soup on the right, side dishes centered. He picked up his chopsticks and paused.
“I’ll be direct,” he said. “I came to SNU today specifically to find you.”
“Me? Why?”
“Because I monitor the contest registration lists, and your name appeared two weeks ago. I didn’t recognize it—which is unusual, because I know every competitive programmer in Korea who’s any good. So I asked around.” He ate a precise bite of rice. “And what I heard was interesting.”
“What did you hear?”
“That you’re a sophomore nobody’s heard of who somehow knows more about computer architecture than most professors. That Kim Taesik—Kim Taesik—personally recruited you for his research lab. And that you’ve been doing practice problems in the SNU computer lab every weekend, but nobody’s seen your solutions because you delete them when you’re done.”
Dojun set down his chopsticks. “You’ve been asking a lot of questions.”
“I always research my competition.” Seokho’s eyes were sharp and direct—no hostility, but no warmth either. Pure analysis. “And you don’t add up, Park. A sophomore nobody’s heard of doesn’t suddenly appear with graduate-level knowledge and a professor’s endorsement. So either you’ve been hiding under a rock for two years, or you’re something new.”
“Maybe I’m just a late bloomer.”
“Late bloomers don’t attract Kim Taesik’s attention. Kim Taesik only notices prodigies. And prodigies don’t hide.”
The cafeteria noise swirled around them—trays clattering, conversations overlapping, the rhythmic beep of the card payment machine. But at their corner table, it felt like a different space. A pocket of quiet intensity.
“What do you want, Seokho?” Dojun asked.
“I want to know what I’m up against tomorrow.” He said it simply, without posturing. “I’ve won this contest twice. I’m going to win it a third time. But I’d rather know who’s in the field than be surprised.”
“And if I told you I’m just a sophomore trying to win some prize money?”
“I’d say you’re underselling yourself, and I’d wonder why.” He finished his rice, aligned his chopsticks on the tray, and stood up. “Good luck tomorrow, Park. I mean that sincerely.”
“Good luck to you too.”
Seokho picked up his tray. “One more thing. When we compete tomorrow—and I say ‘we’ because I have a feeling you’re going to be near the top—I don’t want you to hold back. If you’re good, show it. There’s nothing more insulting than an opponent who doesn’t try.”
He walked away without waiting for a response, depositing his tray at the return station with the same precise efficiency, and disappeared through the cafeteria doors.
Dojun sat in the sudden vacuum of his absence, bibimbap cooling, mind racing.
Seokho had come to SNU to scout him. Had researched him. Had identified the inconsistencies in his story. And had essentially told him: I see you. Don’t pretend to be less than you are.
It was exactly what Seokho would have done. Forty years from now, Seokho would use the same approach in business—direct, surgical, respectful but relentless. He didn’t play games. He played chess, and he expected his opponents to play at their best.
“There’s nothing more insulting than an opponent who doesn’t try.”
Dojun stared at his bibimbap. His careful plan—solve four problems, skip the fifth, finish second—suddenly felt cowardly. Not because winning mattered more than his strategy, but because Seokho had just asked him, in the most direct way possible, to be honest.
And honesty was the one thing Dojun couldn’t afford.
Or could he?
He picked up his chopsticks and ate the rest of his bibimbap slowly, thinking. The cherry blossoms outside the cafeteria window were a little more open than yesterday, pink edges pushing through green buds. By next week, the campus would be covered in petals.
What if I solved all five? the reckless part of his brain whispered. What if I stopped pretending and just… competed? Really competed?
Then everyone would know, the cautious part answered. A sophomore solving all five problems, including a network flow problem that stumps graduate students? That’s not impressive. That’s suspicious.
But Seokho already suspects something. Kim Taesik already suspects something. Hana already suspects something. How long can you keep pretending before the pretending itself becomes the problem?
He didn’t have an answer.
He finished his food, returned his tray, and walked back to the computer lab. The CRT monitors glowed in their rows, patient and waiting.
He sat down, opened the practice set, and looked at Problem E.
Network flow. Dinic’s algorithm. A problem that his twenty-year-old self shouldn’t be able to solve.
His fingers hovered over the keyboard.
That evening, back in his apartment, Dojun called his mother.
“Did you eat?” she asked, before he could say hello.
“Bibimbap at the cafeteria.”
“The university cafeteria? That’s not food. That’s a food-shaped disappointment.”
“It was fine, Mom.”
“Fine is not good. Fine is what you say about weather, not food.” He could hear the market sounds fading—she was closing up the stall for the night. “How was the tutoring? Did Yuri behave?”
“She’s smart, Mom. Really smart. She just needed someone to explain things differently.”
“Her mother says she hasn’t stopped talking about math since you left. She said—and I’m quoting—’Oppa made numbers make sense.’ I almost cried.”
“Don’t cry over quadratic equations.”
“I’ll cry over whatever I want. I’m your mother.” A pause. “Sangchul says he wants to pay you more. Thirty thousand won per session.”
“Twenty is fine. He doesn’t need to—”
“Take the money, Dojun. You need it. And he can afford it—his wife’s salon is doing well.” Another pause, softer. “You’re doing a good thing, helping family. Your father never—” She stopped herself.
Dojun waited. His mother almost never mentioned his father. The man had left when Dojun was three, disappearing into the fog of Korean family shame, and Younghee had built her entire life around the principle of not needing him.
“Never mind,” she said briskly. “Tomorrow is your computer contest, right?”
“Yes. Starts at 9 AM.”
“Are you nervous?”
He thought about it. The honest answer was no—not about the coding. He could solve these problems blindfolded. What made him nervous was the decision he hadn’t yet made. Four problems or five. Caution or honesty. The safe play or the real one.
“A little,” he said.
“Good. Nervous means you care. Your grandmother used to say, ‘A calm stomach before a big day means a small life.'” She clanked something—closing the metal shutters on the stall. “Win or lose, call me after. I want to know.”
“I will.”
“And eat breakfast before the contest. Real breakfast. Not ramyeon.”
“I promise.”
“I love you, Dojun-ah.”
It still hit him like a wave, every time. This simple sentence that he had gone decades without hearing, that he had been too proud to say first, that his sixty-three-year-old self had whispered to an empty hospital room at the very end.
“I love you too, Mom.”
He hung up and sat on the edge of his bed. Outside, Seoul hummed. Inside, the Compaq Presario’s fan whirred softly, the screen dark, waiting.
Tomorrow morning, he would walk into a room with eighty-seven other programmers, including the most talented competitive coder in Korea. He would sit at a terminal. He would receive five problems. And he would have to decide, in real time, who he wanted to be.
The cautious sophomore who played it safe and won modestly.
Or the man who had changed the world once and wasn’t afraid to start again.
Dojun lay back on his bed and stared at the water-stained ceiling. The stain was still there, shaped like a lopsided heart. He had noticed it on his first night back—a landmark from a life he was rewriting, one day at a time.
What would Seokho do? he wondered. The answer was obvious. Seokho would never hold back. Seokho would solve all five problems, set a record, and walk out without looking at the scoreboard because the scoreboard was for people who needed validation.
What would Hana say? That answer was obvious too. “Don’t edit yourself.”
What would Mom say? “Win or lose, call me after.”
He closed his eyes.
Tomorrow, then. He would decide tomorrow.
But somewhere in the quiet machinery of his mind, beneath the caution and the strategy and the carefully constructed disguise of an ordinary sophomore, a decision was already forming. Not a plan. Not a calculation. Something older and simpler than that.
The desire to stop pretending, even if only for three hours, and remember what it felt like to be the best.