Jiang Yubai was right; the introductory class was about to begin.

Lin Zhixia didn’t want to be late. She grabbed Jiang Yubai’s wrist, pulled him forward, and confided in him: “Jiang Yubai, something happened that’s making me feel really bad. Would you like to hear about it?”

Jiang Yubai responded gently: “What is it? Just tell me.”

Lin Zhixia turned her head and glanced at Lin Zeqiu. Her eyes contained hidden grievance and the shimmer of tears. But after her brother made eye contact with her for a moment, he turned and walked away.

From Lin Zhixia’s perspective, her brother’s classmates quickly caught up with him, and the group’s silhouettes grew increasingly distant, gradually disappearing at the stairwell.

In reality, Lin Zeqiu absently stepped onto the stairs, his hand on the railing. He had been about to look for Lin Zhixia, but then remembered those terrifying nightmares. In his dreams, he was scared out of his wits, and upon waking, his pajamas would be soaked with cold sweat.

Besides, Lin Zeqiu believed that his sister was too young, lacking gender awareness, which was why her relationship with Jiang Yubai was so close.

How could Lin Zhixia allow a boy to tug and pull at her in school, in public? Lin Zhixia needed to understand a principle—in middle school, girls should play with girls, and boys should play with boys. Classmates of different genders must maintain a proper distance.

School wasn’t the right place to educate his sister.

Lin Zeqiu planned to grab Lin Zhixia when they got home and teach her a lesson, making her understand what she should and shouldn’t do.

Lin Zeqiu was still thinking about Lin Zhixia.

Meanwhile, Lin Zhixia had cast aside all distracting thoughts and was resolutely heading toward the lecture hall.

Classes 17 and 18 were nearly all present. Students from both classes sat on the left and right sides of the classroom. The middle column of seats remained empty, like a dividing line separating the two competitive classes.

As soon as Lin Zhixia appeared, Han Peng called out to her: “Class Monitor Lin? Class Monitor Lin! Come sit over here with Jiang Yubai! We’ve saved seats for you!”

Lin Zhixia and Jiang Yubai walked over and took their seats one after another.

While other students only brought a notebook, Jiang Yubai carried a heavy backpack. His backpack contained the competition problem set Lin Zhixia had given him—clearly a valuable item. He decided to keep it with him at all times.

No one was maintaining discipline in the classroom, but no one was making a commotion either.

Lin Zhixia lowered her voice and quietly told Jiang Yubai: “That senior student we just met in the hallway, the one who’s about 1.8 meters tall…”

“Who is he?” Jiang Yubai asked casually.

Lin Zhixia honestly introduced him: “That person is my brother, the same-parents kind of brother. His name is Lin Zeqiu, and I’m Lin Zhixia; obviously, we’re siblings. He represents autumn, and I represent summer… I don’t understand why he won’t acknowledge our blood relationship. This morning, he warned me not to call him ‘brother’ at school. He pretended not to know me in front of his classmates and treated me like a junior student from the first-year competition class…”

Fiery anger burned in Lin Zhixia’s heart, consuming all her emotions, leaving only indignation in the ashes: “Why would he do this? Does he hate me? I’m so angry! We grew up together! He always complains that I’m annoying, says I talk too much, and scolds me for wasting his time! I’m not going to pay any attention to him anymore!”

“Lin Zeqiu often scolds you?” Jiang Yubai emphasized this point.

“Not exactly,” Lin Zhixia rested her chin on one hand. “I don’t know how to explain it… Oh, I know now. He just speaks harshly. I remember every word he’s ever said to me.”

Jiang Yubai thought for a moment, then rationally concluded: “Don’t blame yourself. Lin Zeqiu needs to adjust his behavior. My father says you shouldn’t get angry with family members; everything can be discussed with family.”

“What if discussion doesn’t work?” Lin Zhixia humbly asked.

Jiang Yubai calmly said: “Banish them from the home.”

Lin Zhixia was intimidated by Jiang Yubai’s demeanor. She gained a whole new understanding of his father’s parenting methods.

At the same time, she felt increasingly troubled and depressed. The “banishment” method definitely couldn’t be used—it was too cold-blooded and terrifying. So what could be done? She really couldn’t understand her brother’s strange, peculiar mental processes. Would she and Lin Zeqiu be strangers from now on? How should she face her brother when they went home at noon today?

Jiang Yubai suggested: “If you have time, find an opportunity to talk with Lin Zeqiu.”

“Talk?” Lin Zhixia asked. “You mean I should initiate communication with him?”

“Yes,” Jiang Yubai affirmed.

Lin Zhixia shook her head frantically: “No, no, no, you don’t understand…” She leaned on the desk and spoke softly: “He doesn’t acknowledge me now, doesn’t like me, and he’ll be super fierce with me. I hate it when my brother is fierce with me.”

Jiang Yubai’s finger lightly tapped the desk: “He might have something to tell you. Have your father listen in, and he won’t dare be fierce with you.”

“My father is different from yours,” Lin Zhixia explained. “My father is very gentle. My brother doesn’t have a sense of awe toward him. However, my brother is obedient at home; he sweeps the floor, mops, washes dishes, and does laundry. The washing machine at our home is a twin-tub… You know? One tub for washing and another for spinning.”

Jiang Yubai knew nothing about housework. His hands had never touched a drop of water; he’d never done any dirty or tiring chores. But he understood that Lin Zhixia’s brother contributed a lot to their family. Thinking about this, Jiang Yubai’s impression of Lin Zeqiu improved a tiny bit.

But only a tiny bit.

Jiang Yubai believed that as an older brother, Lin Zeqiu should set a better example. Even if Lin Zeqiu genuinely disliked Lin Zhixia, he shouldn’t constantly say “sister is annoying.”

Jiang Yubai’s father had once told his son, a mature man should have depth, breadth of mind, and spirit, not letting others easily guess his thoughts. It was clear that Lin Zeqiu wasn’t mature enough, and Jiang Yubai hoped he would grow up.

After thinking it through, Jiang Yubai reluctantly said something positive about her brother: “Lin Zeqiu has a strong sense of family responsibility.”

Then, Jiang Yubai continued to comfort Lin Zhixia: “When you talk to Lin Zeqiu, appeal to his emotions, explain with reason, and ask him why he’s pretending not to know you.”

The guidance counselor had already entered through the main door.

This guidance counselor was probably in his fifties. His hairstyle was rather distinctive—sparse hair formed a ring around his head, while the center of his scalp was completely bald. Several students from Class 18 whispered among themselves, secretly nicknaming the guidance counselor “Mediterranean.”

The guidance counselor noticed the students in the front row making fun of his hairstyle. But he showed no sign of minding. He coughed once and spoke at a moderate pace: “Students, raise your heads. You should listen carefully to this introductory class, as it concerns your choices for the next three years and your development path in Provincial No. 1 High School’s competition class. The first slide of my PowerPoint contains a 126.com email address and password. I’ve uploaded the competition class training introduction documents and overview materials as attachments to this email. When you get home, if you have the means, you can go online and download the electronic version. The school will also provide you with printed versions, and you can take them out to read and review whenever you have time, okay?”

“Okay!” Lin Zhixia cheered quietly.

Lin Zhixia had just resolved her inner conflict. Jiang Yubai’s analysis and advice had been very helpful to her, and he had also passed courage to her courage.

When she got home today, she would talk to her brother! Just as Jiang Yubai said, she should try first, regardless of the outcome.

Lin Zhixia secretly summarized in her heart: Jiang Yubai fears nothing, Jiang Yubai is clear and logical, Jiang Yubai is knowledgeable and experienced, Jiang Yubai is indeed Lin Zhixia’s eternal friend, her best friend.

He could listen to her confide in him, help her plan, and give her advice, which made her feel very secure. The emotional value he brought was always positive. In Lin Zhixia’s memory, Jiang Yubai’s every move and every word had never hurt her.

Lin Zhixia suddenly realized: “No wonder, no wonder…”

Jiang Yubai was taking notes while asking: “What do you mean, ‘no wonder’?”

“No wonder I feel happy every time I see you,” Lin Zhixia analyzed rationally and calmly. “I’m just an ordinary deep learning neural network, and my objective function is to make my life happier. When I lean toward you, I receive positive feedback, so I’ll keep getting closer to you.”

Jiang Yubai’s handwriting was neat and fluid. He looked forward and made a request: “Lin Zhixia, please speak human language.”

Lin Zhixia immediately spoke human language: “You’re really good.”

Jiang Yubai’s pen tip paused.

Lin Zhixia worried he wouldn’t understand. She emphasized again: “You’re especially good. Even though there are many things in life we want but can’t have, at least meeting you is something rare and precious. Friendship between friends is priceless.”

After speaking, Lin Zhixia nodded.

Jiang Yubai had crumpled the page of his notebook in his grip. He lowered his head and raised one side of the notebook to hide half his face. He thought he was contemplating “competition class training modes,” but what his pen recorded was “friendship is priceless.”

Last year at Experimental Elementary School, Jiang Yubai had already received the evaluation of “you’re super amazing.”

Today in Provincial No. 1 High School’s lecture hall, Jiang Yubai heard “you’re really good, you’re especially good…” and a string of other words he was too embarrassed to recall in detail.

Perhaps Lin Zhixia was both his competitor and his true friend. These two identities weren’t contradictory; they could even encourage him to continuously improve himself.

Jiang Yubai’s fighting spirit was ignited.

He noted down the competition class’s teaching methods, students’ course directions, and cultivation projects from previous years. This weekend, he would discuss strategies with his tutoring team and quickly develop an effective plan. He wanted to advance alongside Lin Zhixia, sweeping awards across the province, nation, and even globally.

On the podium, the guidance counselor stood with his hands behind his back, gazing at the many students in the competition class.

The slide show reached the final slide. This introductory class was nearly over. The guidance counselor hadn’t taken too much time. His lecture was skillful, with appropriate detail and emphasis, leaving a deep impression on the students. One of his life principles was not to waste words on students.

All the students were looking at him.

Those students had young faces. One day, they would grow up to be pillars of the nation.

“Alright, everyone, attention,” the guidance counselor announced loudly. “Next, please welcome with applause your homeroom teachers from Class 17 and Class 18—Teacher Zhang! Teacher Wang!”

A wave of enthusiastic applause erupted inside the lecture hall. The momentum was immense, like surging waves stirring up thousands of layers of water, breaking the originally calm atmosphere.

Teacher Zhang and Teacher Wang both walked onto the podium.

Class 17’s homeroom teacher, Teacher Zhang, bent down to control the mouse and opened a Word document named “Math Warm-up Quiz.” The document contained forty small problems, each occupying one page.

Class 18’s homeroom teacher, Teacher Wang, pulled out a small whiteboard. He picked up a black marker and wrote on the whiteboard: Class 17, zero points. Class 18, zero points.

Teacher Wang briefly introduced the competition rules: “Students! These are quickfire questions. Answer correctly to earn one point, answer incorrectly to lose one point. If a student from one class answers incorrectly after buzzing in, we’ll pick another student from the other class.”

Answer incorrectly and lose points?

Hearing this bad news, the students all became more cautious. Some even decided not to participate in the competition to avoid dragging down the collective, maintaining silence from beginning to end. Even if they remained mute, it would be better than being “one bad apple spoiling the whole barrel.”

Class 17’s homeroom teacher, Teacher Zhang, revealed a knowing smile. He stood up straight, displayed the first question from the Word document, and read aloud: “What are the interior and exterior angles of a regular octagon?”

Lin Zhixia immediately raised her hand.

But a female student from Class 18 suddenly stood up and directly answered: “Interior angle 135 degrees, exterior angle 45 degrees, sum of interior angles 1080 degrees.”

This female student wore glasses, had short, ear-length hair, dressed neatly, and her appearance wasn’t particularly noticeable. Her tone of voice was very steady, like a vast river without waves.

Teacher Wang gently criticized her: “Jin Baihui, you should raise your hand first. Wait until we call on you before standing up. Respect the game rules…”

Teacher Zhang, on the contrary, did her a favor: “Oh? Is she Jin Baihui from Class 18? It’s fine. Jin Baihui’s mental calculation is very fast; other students might not be stronger than her. Let’s proceed! Class 18 earns one point.”

Why should that be allowed?

Lin Zhixia muttered, “I can do mental calculations too. I’m faster than her.”

Shen Fuxuan hissed and said quietly: “Jin Baihui! That’s Jin Baihui!”

Lin Zhixia asked: “Who is Jin Baihui? Is she that impressive? Her name didn’t appear on the entrance exam ranking list.”

“She was ranked first last year. Don’t you know?” Shen Fuxuan turned to Lin Zhixia and said, “Jin Baihui took Provincial No. 1 High School’s middle school competition class entrance exam last year. She also got into a gifted children’s class in Beijing. She went to Beijing to study for most of the year but didn’t adapt well…”

“So Jin Baihui returned to Provincial No. 1 High School?” Jiang Yubai inquired.

“Yes,” Shen Fuxuan covered his mouth with one hand and secretly told them, “Class 18’s homeroom teacher values Jin Baihui highly. I heard from my mother that Class 18’s homeroom teacher would rather give Lin Zhixia to Teacher Zhang than not take Jin Baihui as a student.”

“Your mother? How does your mother know what Class 18’s homeroom teacher thinks?” Lin Zhixia noticed this point.

Shen Fuxuan stretched out his legs, sitting like a lazy old man. He answered without any evasion: “My mother is the principal of Provincial No. 1 High School. I chose to be in Class 17 myself. You’re ranked first, so wherever you are, that’s where I want to be. If you had gone to Class 18, I would have followed you there.”

His mother is the principal of Provincial No. 1 High School…

So his grandmother must be Professor Shen Zhaohua?

Lin Zhixia finally understood the causal relationship and was extremely surprised. She learned quite a bit of inside information from Shen Fuxuan. Her interest in Jin Baihui increased.

While Lin Zhixia, Jiang Yubai, and Shen Fuxuan were chatting, Teacher Zhang announced another question. That question was also answered by Jin Baihui after she raised her hand. Her mental calculation ability was indeed formidable.

Class 17 was behind by two points.

Jin Baihui glanced sideways at the students of Class 17. Her chin tilted slightly, her expression cold, full of provocation.

Jin Baihui’s seat was close to the dividing line between Class 17 and Class 18. And Duan Qiyan happened to be sitting nearby.

Duan Qiyan folded his arms, secretly glancing at Jin Baihui. Jin Baihui held up her little finger to him, nearly causing him to explode with anger on the spot.

All these little actions were seen by Teacher Zhang.

Teacher Zhang unhurriedly read: “Question three: In an arithmetic sequence where the first five terms are all prime numbers, what is the minimum possible value of the fifth term?”

Jin Baihui raised her hand high.

But Lin Zhixia stood up and answered: “The minimum value of the fifth term is 5. The arithmetic sequence is 29, 23, 17, 11, 5.”

Teacher Zhang smiled and said: “Lin Zhixia, you’re correct, but you should raise your hand first.”

Lin Zhixia perfunctorily apologized: “I’m sorry, Teacher. I was too eager. Next time I’ll raise my hand.”

Teacher Wang smoothed things over: “You’re Lin Zhixia from Class 17? Very good, very good. Although I didn’t interview you, other teachers all spoke highly of you. We expect you to bring honor to Provincial No. 1 High School. Good! Class 17 gets one point. After this round, everyone must raise their hands! We must respect the rules, okay?”

All the students agreed in unison.

Teacher Zhang scrolled the mouse wheel, and Teacher Wang read out the fourth question: “Students, listen carefully. Suppose n is a single-digit decimal number, and there is another three-digit decimal number. This three-digit number is represented as nq in base 58 and as (n-1)g in base 62. What is this three-digit number?”

Jiang Yubai was the first to raise his hand.

Lin Zhixia noticed his movement and didn’t compete with him. She began to worry whether Jiang Yubai could answer correctly. She held her breath and heard Jiang Yubai say: “The three-digit number is 512, and n equals 9.”

Lin Zhixia extended two index fingers and tapped their pads together, quietly applauding him.

Teacher Zhang happily praised: “Excellent! The answer was both quick and correct! Class 17 gets another point! Originally, Teacher Wang and I were concerned that the questions might be too difficult to stimulate everyone’s enthusiasm, but now we see that students from both our classes are enjoying themselves! Very good! Keep up this momentum!”

Han Peng, sitting in front of Lin Zhixia, couldn’t help saying: “I give up… So far, only Jin Baihui, Lin Zhixia, and Jiang Yubai have answered questions, yet Teacher Zhang thinks we’re all enjoying ourselves.”

Han Peng leaned back against his chair, tilted his head back, and asked Jiang Yubai: “How did you solve that last question?”

“Quick base conversion,” Jiang Yubai replied. “It’s quite basic.”

Jiang Yubai had learned base conversion two years ago and had spent six months this year intensively practicing mental and oral calculations. Even though he had played all summer, he still maintained his mathematical foundation.

“That’s right, Jiang Yubai is correct; that kind of conversion is pretty basic,” Lin Zhixia especially agreed with his words.

Han Peng stretched his neck and nearly choked. He steadied himself by holding the desk, lowered his head, and coughed frantically.

Life is too difficult, Han Peng thought.

Meanwhile, the competition continued. Lin Zhixia gradually felt the unfairness. She was always the first to raise her hand. But sometimes, Teacher Wang wouldn’t call on her; Teacher Wang tended to call out “Jin Baihui’s” name. The first-year math warm-up quiz wasn’t too difficult, with almost no particularly complex knowledge points, so it wasn’t surprising that Jin Baihui could solve them.

“Can an unfair competition even be called a competition?” Lin Zhixia wondered.

Jiang Yubai had already seen through everything. He enlightened Lin Zhixia: “The guidance counselor is sitting at the back of the classroom. Teacher Wang can’t let the guidance counselor think Class 18 is much worse than Class 17. When you and Jin Baihui raise your hands one after another with only a two-second gap, it’s not very obvious. Also, if Class 18 loses too badly, it would crush their morale, which isn’t good for building confidence.”

Lin Zhixia lay on the desk. She unilaterally forfeited, expressing silent protest.

Her cheek pressed against her arm, making her look both pitiful and cute.

Jiang Yubai noticed Lin Zhixia’s state, and his heart filled with a sense of mission. He discovered that Teacher Wang deliberately ignored Lin Zhixia, which was equivalent to a referee on a basketball court intentionally showing favoritism by blocking the opposing team’s star player.

He had seen this kind of plot in “Slam Dunk.”

He remained undaunted and responded calmly.

Teacher Wang continued reading questions: “When rolling a die, add up the points on the die. If the total exceeds 10,000, it counts as a failure. If the total equals 10,000, it counts as a success. If the total is less than 10,000, continue rolling the die. What is the probability of success?”

The classroom fell silent for over ten seconds. Then Jiang Yubai and Jin Baihui raised their hands simultaneously.

Before Teacher Wang could speak, the guidance counselor sitting in the last row said: “I see these two students raised their hands almost at the same time. Let them both answer. Today we’re holding a small competition, not some major contest. Friendship first, competition second.”

Teacher Wang first asked Jiang Yubai: “What’s the probability?”

Jiang Yubai answered composedly: “Two-sevenths.”

Jin Baihui suddenly spoke up, questioning Jiang Yubai: “How did you calculate that? Your method isn’t as fast as mine. I can set up an equation to get the result of two-sevenths.”

Teacher Wang nodded repeatedly: “What equation? Jin Baihui, come to the blackboard and write it out for everyone to see.”

Jin Baihui’s face seemed covered with a layer of frost, with coldness and arrogance coexisting. She cared about winning and losing more than Jiang Yubai did. She wrote on the blackboard: “Rolling a die six times, the expected value is three and a half. I’ll first use the formula to prove that the sequence eventually converges…” She realized her logic wasn’t rigorous enough and immediately applied L’Hôpital’s rule.

Just as Jin Baihui was about to state her conclusion, Lin Zhixia’s voice drifted over: “This question isn’t difficult, and I believe you can solve it quickly. But I think you don’t need to write out the general term formula. In Blackwell’s key renewal theorem, there’s a case called the lattice case, and the dice-rolling game perfectly meets its constraint conditions. In this case, each term of the random variable can be expressed by dividing a constant by the expected value. The constant for the dice game is one, so the result is one divided by three and a half, which equals two-sevenths.”

Jiang Yubai remained silent.

Because his method was the most basic.

He assumed the probability of success was p and the probability of failure was (1-p), and the various failure scenarios could be completely enumerated. For example, one scenario would be when the cumulative total of the die reached 9,995, and rolling any number other than 5 would mean a loss… By continuing this reasoning, he could also calculate the answer.

The mathematical theorems that Jin Baihui and Lin Zhixia applied were much more complex than his.

Yet Teacher Zhang said: “Jin Baihui’s method is very rigorous, showing a solid grasp of advanced mathematics concepts. I also appreciate Jiang Yubai and Lin Zhixia’s methods; Blackwell’s renewal theorem is concise and powerful.”

Lin Zhixia nodded proudly.

Sitting in her seat, she quietly extended a hand downward. Jiang Yubai copied her gesture, and she seized the opportunity to immediately high-five him.

Jiang Yubai was greatly encouraged. He lowered his head and smiled silently.