A butterfly in the tropical rain forest near the Amazon River in South America occasionally flaps its wings, which may cause a tornado in Texas, USA two weeks later.

This is the famous "butterfly effect", and it is also the reason why Lin Chaoxi is now in great trouble.

She studied philosophy, and in her previous logic class, the teacher spent the entire class explaining the "butterfly effect," saying that it was a slippery slope fallacy because it directly transformed possibility into inevitability.

Of course, butterflies in the Amazon rainforest do not necessarily cause hurricanes in Texas. What it actually refers to is the chaos theory. It is the possibility that a small change under the initial conditions can lead to a long-term and huge chain reaction in the entire system.

The same is true for transportation.

If she wanted to predict the specific location where Lao Lin would have a car accident within a certain period of time, she would have to take the entire traffic system into consideration. However, there were so many factors to consider that it gave her a headache.

At 5 o'clock in the morning, the alarm clock beeped softly. Lin Chaoxi woke up in a second and quickly turned it off.

But Xiaolin, who was lying on the bed opposite, turned over twice, and the painful and suppressed sound rang out again. Lin Chaoxi knew that she had woken up again.

In order to get out quickly every day, she would change into clothes for the next day before going to bed. Now, she immediately got up from bed, picked up her backpack, and went out quickly.

Yongchuan has been experiencing sauna weather for a week, and today's sky is particularly gloomy. Lin Chaoxi looked up at the morning sun, which had lost its original power due to being suppressed by the thick clouds, and felt that it was time for a heavy rain.

She was absent-minded during her first exam in the morning. Maybe it was because her period came. She felt sleepy, cold and tired. She forced herself to be awake, but all she wanted to do was lie on the table and take a nap.

If Jie Ran hadn't knocked on her desk in a friendly manner, she would probably have fallen asleep on the desk during the exam for the first time in her life.

When handing in the paper, Lin Chaoxi felt bad.

Xie Ran took a look at her test paper and asked her if she wanted to see a doctor.

Before she could answer, Lu Zhihao said, "I'm sure every girl has those days. It's okay."

Lin Chaoxi was stunned for a moment, then forced herself to joke with him: "You really are my good sister."

"I'd better go there at noon." Xie Ran said again.

"Well, thank you, teacher."

——

In fact, from Jie Ran's eyes, Lin Chaoxi roughly knew that her test results must not be ideal.

But when the test papers were handed out, she still couldn't accept the excellent score of 59.

Chang Shu Ping said at the podium: "This exam was quite difficult. No more than ten students scored above 60 points. This was my own mistake in setting the test paper. I hope everyone can have a positive attitude and not think that they have failed the exam."

“It’s too difficult.”

“I can’t even do the last question!”

The students below complained one after another.

"Lin Youguang scored 90 points in the exam. This is an excellent performance and deserves encouragement."

There was sparse applause in the classroom.

Lin Chaoxi was still looking at her own score. She only got a few points on such a difficult test, but A Guang scored 90 points, and now, 10 people have surpassed her.

After everyone was pulled to the same starting line, the importance of talent gradually became apparent. For her, Mathematical Olympiad was still very difficult.

"At the same time, I would also like to remind you that some of the students who previously ranked at the top did not perform very well in this exam. I hope you can adjust your schedule and take good care of your health. This is more important than studying hard."

Hearing this, Lin Chaoxi raised his head suddenly.

There was a little noise coming from the high school students. Someone pushed Yin Xiaolin and said something with his head down.

Probably - look how hard she works every day, yet she still fails the exam.

In fact, Lin Chaoxi didn't want to care about these words. She had heard a lot of similar sarcasm.

But at this moment, perhaps due to physical and mental fatigue, many thoughts that she had never agreed to seemed to emerge.

"Only 5% of people are suitable for the Mathematical Olympiad", "People without talent should not waste their lives on mathematics", "In the end, mathematics is a competition between geniuses."

She suddenly wondered if she really needed to stay here.

Time was tight, and she probably couldn't do several things at once. More importantly, she might not be the kind of genius who was suitable to stay in this field until the end, and there was no need for her to receive too rigorous training.

——

I was completely confused during the class.

After class, Lin Chaoxi picked up his backpack and prepared to go to the library to read.

She had not taken a few steps when someone called her from behind.

"Lin Zhaoxi!"

It was Lu Zhihao's voice.

The sky outside the corridor was completely dark and it looked like a rainstorm was about to begin.

Lin Chaoxi and Lu Zhihao stood face to face. There were obviously many people around them, but she felt that everything was empty. It was a bit like the time when she desperately chased Lu Zhihao at the summer camp in elementary school.

"Are you too tired recently?" Lu Zhihao asked.

"You know, girls have those days every month," she said nonchalantly.

"I think you should take a break. How about I ask Pei Zhi when he can come over, and we can go out for dinner and relax or something?"

When Lu Zhihao was anxious, his face would be visibly wrinkled. Although he pretended to say it casually, Lin Chaoxi could still see it.

"I don't have time to go out recently. Let's go later. Can you also invite Hanajuan?"

She was still chatting, but had already started to leave. Lu Zhihao tried to pull her back, but she broke away from him and ran downstairs.

Lin Chaoxi knew when her self-esteem became so strong. She didn't feel too bad when she did poorly on the exam, but when Lu Zhihao held her back and comforted her a little, she actually felt like crying?

Rubbing her nose, she walked into the reading room.

During the summer vacation, there were still many graduate students and doctoral students sitting in the library of Sanwei University, as well as students who wanted to prepare for postgraduate entrance examinations. Especially at this time, no one went to eat, and the reading room was surprisingly packed.

She took a book from the bookshelf, found a corner, and sat down cross-legged.

This is a book called "Linear Algebra". It was published a long time ago and the pages are yellowed, but it is on Lao Lin's book list.

Lin Chaoxi took it unconsciously. Perhaps subconsciously, looking at Lao Lin's handwriting and jokes made her feel better.

Maybe it was because, among the adult college students, she, a junior high school student sitting on the ground, was still very conspicuous.

She was soon accosted.

"How old are you?" A short-haired female college student looked at her.

"ah?"

"Linear Algebra. Why are you reading this book?"

Lin Chaoxi was slow to react today. Just when she was thinking about how to answer, the female college student looked away and opened her book to read.

Lin Chaoxi took a quick glance and found that the book she was reading was also covered with various annotations. If she had no problem understanding it, it was a book on Differential Geometry.

"Do you think it's strange that both of our books have annotations?" the female college student asked her quietly. "Who asked you to borrow this book, or did you just take it randomly?"

"It's my father."

"I knew that most people would have put down a book with such random writing and drawings." She smiled. "Is your father a professor of mathematics? Can you tell me who he is and give me a back door? I want to take the postgraduate entrance examination next year."

“No…it’s not that.”

"That's the senior."

Lin Chaoxi was wondering what kind of strange habits the Department of Mathematics at Sanwei University had. Whether it was Jie Ran or this female college student, they wanted to come over to claim relationship with her just because they saw her holding a book full of annotations.

She pondered for a moment: "How can you be so sure that he is a senior?"

"Since he is not a teacher but only a senior, why else would he let you read this book? And you are so young, but your father only let you read Linear Algebra?" The other party paused and said, "No, if your father is not a teacher, then how do you have a debit card for our school? Is it your grandfather?"

"No." Lin Zhaoxi explained, "I'm training here."

"From the provincial math competition team?"

"Um……"

"Little genius!"

This was the first time that Lin Chaoxi was associated with this word. If it was before, she would probably be a little happy, but today she was just brought back to her true colors and she couldn't be happy at all.

"Is there anything special about this book?" she asked after closing the book.

"This is a tradition in our mathematics department. Everyone will secretly write about interesting things and exchange ideas. Teachers educate students, seniors educate juniors, and the older generation passes on knowledge to the younger generation."

"Tradition? The school is very tolerant of the mathematics department."

"Of course we tolerate it. After all, it is the top major in the country. But it is said that the school was opposed to it at first. It was the teacher who led such students to do it. He also used Fermat's "Arithmetic" as an example, saying that the flash of inspiration of mathematicians is very important. The school thought it made sense and didn't care..."

When Lin Chaoxi heard the word Fermat, his heart beat very fast: "Teacher... do you know the name of that teacher? Is he still in school?"

"It's not clear what it was called, but it was said that the teacher left the school soon after."

Lin Zhaoxi's palms were a little wet: "Why did you leave?"

"I don't know. You're asking so much, could it be your father?"

"I have no idea."

"Why don't you know this?" The young lady pointed to the ceiling. "There is a school yearbook in the library upstairs. You can look up the names of graduates there. If you know how old your father is this year, you can calculate the age when he graduated from college, graduate school, or got a doctorate. You can find it by flipping through the yearbook."

Lin Zhaoxi: “…”

"And the book you have is so old. Generally, teachers who have just come to our school for exchange won't read this book, so your father is most likely a senior student from the 1990s."

Lin Chaoxi remained silent.

People in the mathematics department have clear ideas. They use their own age to calculate graduation age, and then look up yearbooks. Of course, she has thought of these methods, but she has never thought about it in this way.

She stood up immediately, walked out of the circulation room quickly, and handed the book to the circulation desk. After the staff scanned the book, the bar code made a slight "beep" sound, and she came back to her senses.

But next, she didn't go directly to the filing room.

She looked around the library lobby, walked to the book search machine, and took out the note that Lao Lin had written to her from her schoolbag.

There were familiar handwriting and many book lists on it, and the paper was wrinkled from having been read so many times.

She had felt strange before. She flipped through the books that Lao Lin told her about and found that they were yellowed due to age.

And after the female student reminded her to look at the publication date, she roughly guessed why.

She clicked on the search box and began searching for books by title.

1990

1992

1987

…

Lin Chaoxi kept checking and looking at the publication date of each book. When she finished, she silently released the mouse.

In the list of books that Lao Lin gave her, not a single one was published after 1994.

The year she was born.

That is to say, after she was born, Lao Lin never read any book in the Sanwei University Library.

Lin Chaoxi let go of the mouse and took a step back.

Several dragonflies flew into the library and circled in the low air. A thunderclap sounded outside the library, and Lin Chaoxi felt weak and confused from the inside out.

Strawberry World, Lao Lin left school for her.

But why in this cheese world that once did not have her, Lao Lin also left school and his mathematics job at the same time, and even gave up the opportunity to study abroad...

Why is all this happening?