My IQ has been increasing year by year.

In late August, Huizhou finally sheds the oppressive heat that had been suffocating people.

For the first time ever, the morning and evening breezes carried a hint of coolness.

The leaves of the trees outside the old library window were beginning to turn slightly yellow at the edges. Occasionally, a leaf or two would twirl down and fall onto the floor tiles when the wind blew. In the foreign language reading room on the third floor, the ceiling fan was still stubbornly spinning, but the air it blew was no longer the kind of hot, irritating draft. Chen Zhuo sat in his usual spot by the window, flipping through a thick algebra book.

He didn't read quickly, sometimes spending more than ten minutes on a single page, occasionally tapping his pencil on the draft paper beside him to jot down a few dry characters. Across a large wooden table, Su Wei sat diagonally opposite him.

"Smack."

The sound of the book closing, though not loud, was crisp and decisive, breaking the silence in the corner.

Chen Zhuo raised his head.

Su Wei was pressing her hand on the cover of the thick book, "Probability Theory and Mathematical Statistics".

The book is now in a truly appalling state.

The once sturdy spine was now completely limp from repeated readings, the edges were frayed, and the cover was even reinforced with two layers of transparent tape. The pages, due to countless flips and notes, had become almost a third thicker than before, and viewed from the side, they were densely covered with creases and marks from black ballpoint pens. Su Wei let out a long sigh.

She didn't speak immediately, but instead raised her hands and pressed her thumbs firmly against her temples and eye sockets, as if trying to force all the numbers and formulas she had crammed into her brain over the past two months to settle. Chen Zhuo put down the pencil in his hand and leaned back in his chair.

"All done?"

He asked softly.

Su Wei lowered her hand and opened her eyes.

Her eyes were bloodshot, the price of prolonged, intense concentration, but at this moment, they shone with an intense brightness, a triumphant satisfaction after completing some arduous battle. "The last chapter, parameter estimation and hypothesis testing, is finished."

Su Wei's voice sounded a little hoarse because she hadn't spoken for a long time.

"How are you feeling?"

"At first, it felt like gnawing on pig iron."

Su Wei picked up the water glass on the table and took a sip of the already cold boiled water.

"Later, using the matrix dimensionality reduction method you taught, after breaking down all those continuous integral formulas into discrete grids, it's like finding a crack in pig iron, and you can directly use a hammer to smash it open along the crack." She paused, looked at Chen Zhuo, and her tone carried a rare hint of admiration.

"Your method is really useful. It saved me at least half of the computation. Many continuous probability density functions that originally required a lot of detours to find derivatives can be directly reduced to simple addition, subtraction, multiplication and division after you cut them into matrices. You are very clever."

"As long as it works, that's fine."

Chen Zhuo smiled.

"The continuous calculus taught in textbooks is for pursuing absolute mathematical rigor and perfection, but you learn it to calculate financial models and assess risks in the future. Pragmatists don't need perfection, they just need a knife that is fast and sharp enough."

Su Wei nodded in deep agreement.

She carefully put the nearly falling textbook into her faded canvas bag and zipped it up.

Then, she took a somewhat worn coin purse from her pocket, unfastened the snap, and carefully took out two one-yuan coins, placing them in her palm. "Let's go."

Su Wei stood up and pushed the chair back under the table.

"Where to?"

Chen Zhuo raised an eyebrow.

"Come downstairs, I'll buy you a soda."

Su Wei looked at him, her tone calm, but her eyes were serious.

"Consider it a thank you for your help this summer. Without the paths you drew, I probably would have died from this book this summer." Chen Zhuo was taken aback.

He turned his head, glanced at the sky outside the window as if to make a show of it, and then turned back to look at Su Wei.

"It's not snowing outside today."

He said it in a very serious tone.

All summer long, Su Wei was extremely stingy. She would use every pen refill she could possibly write with, and her draft paper was covered in writing on both sides. For Su Wei to buy someone a soda was indeed rarer than snow falling in August.

"Stop talking nonsense." Su Wei ignored his teasing. "Two yuan budget, are you going to drink or not? If not, I'll take it back."

"Drink it, you're such a tightwad, you'd be a fool not to."

Chen Zhuo smiled, stood up, closed the book on the table, casually tucked the draft paper between the pages, and picked up his own things.

The two walked out of the reading room one after the other.

The light in the corridor was dimmer than in the reading room, and the air was filled with the smell of old books.

As you walk down the stairs, you can faintly hear the sounds of basketballs being played on the playground outside the building.

Stepping out of the old library, the cool evening breeze blew in, dispelling the musty smell of books that had lingered inside all afternoon.

The sun had already set behind the buildings in the west, and the sky was tinged with a soft orange-red.

The main road on campus gradually became more crowded, mostly with students who stayed on campus to return to their dormitories or walk in twos and threes toward the cafeteria. They walked along the path toward the dormitory area.

There was a small shop by the roadside. The owner was sitting on a small stool by the door, fanning himself with a palm-leaf fan, while a radio next to him played storytelling by Shan Tianfang. Su Wei walked to the freezer and opened the glass door.

A burst of white, cold air instantly emerged.

The freezer was neatly stacked with rows of glass bottles of orange soda, the bottles covered with water droplets.

Su Wei took two bottles, walked to the counter, and placed the two one-yuan coins she had been holding in her hand on the glass.

It made two crisp, ringing sounds.

"Uncle, open it for me."

The boss slowly stood up, picked up a metal screwdriver tied to the side of the cabinet, and skillfully pried open the bottle cap.

"Sizzle"

"Sizzle"

Two sweet orange scents wafted out from the bottle opening.

Su Wei handed one of the bottles to Chen Zhuo.

The glass bottle was very cold; you could feel the chill when you held it in your hand.

Chen Zhuo took the soda, tilted his head back, and took a big gulp.

The icy liquid slid down my throat into my stomach, the tingling sensation of the carbon dioxide bubbles bursting on my tongue sending a shiver down my spine. But on this late summer evening, it felt just right.

"Cool."

Chen Zhuo sighed.

Su Wei also took a small sip, drinking very slowly.

The two did not leave immediately, but instead walked to a flower bed next to the convenience store and stood there.

The flower bed was edged with white tiles. Chen Zhuo leaned against the tiles, watching the streetlights gradually come on in the distance.

"What are your plans next?"

Chen Zhuo looked at the glass bottle emitting cold air in his hand and asked casually.

"I've finished studying probability theory, what new subject am I going to move on to?"

"No rush to eat new dishes."

Su Wei shook her head.

"I need to spend some time putting these theories into practice with real data. The things in books are ultimately static. When school starts, I'll go to the computer lab to find some real historical stock market data and use your discrete model to build a simple order book to calculate it. Once I get the tools, I'll have to try them out to see how fast they are."

"And you?"

Su Wei turned her head and looked at Chen Zhuo.

"What are you planning to do all summer by writing those symbols that only a devil could understand at that table?"

Upon hearing this, Chen Zhuo lowered his head to look at the soda bottle in his hand, remained silent for a moment, and then chuckled softly.

Rebirth sounds like a huge cheat code in this world, where many people return with decades of memories and become omnipotent. But only Chen Zhuo himself knows best that he was just an ordinary person in his previous life.

His mind wasn't filled with readily available cutting-edge technology, nor did he possess any aircraft engine blueprints, let alone memorize the underlying source code of lithography machines. His understanding of that magnificent future was limited to the grand terms he occasionally gleaned from news reports: chip blockades, algorithmic barriers, materials sanctions, and EDA software bottlenecks. He knew where the key points lay.

He knew that a decade or so later, the other side of the ocean would use its technological hegemony to choke this place.

But he didn't know how to get to that point.

Therefore, he could not, like those gifted and reborn individuals, directly write down epoch-making truths from memory.

His only reliance was on his young, focused, and sharp mind, amplified by his rebirth, and a futuristic perspective that was slightly ahead of his time. Since he didn't have any ready-made weapons in his mind, he could only build the toolkit for them himself, bit by bit.

He meticulously studied every mathematical journal, algebraic topology, and graph theory foundation he could find in the old library, bit by bit. He knew the future belonged to computers, algorithms, and high-tech industries, and the underlying logic of those things couldn't rely solely on traditional egalitarian methods and brute force. This process was tedious, didn't solve any concrete real-world problems, and to outsiders, it seemed he was just drawing meaningless matrix symbols on paper every day. "Me?"

Chen Zhuo took a sip of soda, and the carbonation made him squint slightly.

He turned his head to look at Su Wei, his tone relaxed, as if he were talking about the most ordinary little thing.

"I guess I fired a kiln of bricks for myself."

"Making bricks?"

Su Wei clearly didn't understand the metaphor, and her brows furrowed slightly.

"Um."

Chen Zhuo nodded.

"You study probability theory so you can build a ship and make money during the financial crisis. I'm not as pragmatic as you. I just know that there might be strong winds and heavy rains in the future." He gently tapped the bottom of the bottle against the edge of the flower bed's tiles, making a dull sound.

"I didn't have any ready-made skyscrapers in my mind. I didn't do anything this summer except dig a hole in the ground and use discrete algebra as firewood to burn the scattered mathematical theories and logic that I usually see into solid bricks."

He didn't use any grand vocabulary; he simply attributed it all to making bricks.

Now, this small, unbreakable foundation of discrete algebraic logic has been firmly laid deep within his mind. He doesn't need to memorize any previous conclusions, because with these basic bricks, and as long as the logic is sound, he can build his own skyscraper, layer by layer, to the heavens. Su Wei looked at Chen Zhuo.

She had always felt that the boy in front of her was somewhat contradictory.

He possessed an extraordinary computational ability, capable of calculating probability and expected value with a single glance, yet he always acted with a deliberate and methodical approach, lacking any of the arrogance or impatience typical of geniuses. He was like a bottomless well; if you threw a stone into it, you wouldn't even hear an echo.

"Although I don't understand what you're saying."

Su Wei withdrew her gaze and looked at the sky in the distance, which was gradually darkening.

"But it seems like you've also finished something really tiring."

I guess so.

Chen Zhu shook the glass bottle in his hand; there was still a sip of soda left inside.

Su Wei smiled, a rare occurrence for her.

"That sounds interesting."

She raised the soda bottle in her hand, as if to toast.

"So, it's a pleasure working with you?"

"It's a pleasure working with you."

Chen Zhuo also raised the bottle and gently touched its body.

The glass made a crisp sound.

The late summer breeze swept across the open space where they stood, dispelling the last traces of summer heat.

In the distance, lights began to come on in the windows of the dormitory building.

The old man at the mailroom rode past them slowly on a dilapidated old bicycle, ringing his clear bell.

In a few days, returning students will gradually return to school, and freshmen will also flood into the campus with their bags and luggage.

The school, which had been quiet for two months, was about to become noisy again.

Chen Zhuo tilted his head back and drank the last drop of soda from the bottle.

He let out a long sigh of relief.

Their summer together ended quietly and uneventfully.