From a timeline perspective, it was the summer vacation seven years ago. But for Lin Chaoxi, only less than half a year had passed.

She clearly remembered that in the evening when a rainstorm was about to come, she walked in the dim light in the library of Sanwei University, which was filled with the strong smell of books, trying to find Lao Lin's past.

But nothing was gained.

Now she has come to another century-old school library adjacent to Sanmi University, as if she is about to face all the unsolved answers.

They stood at the door of the data room, panting.

Lu Zhihao was still taking out his card slowly, unsure whether his card could be used to enter the data room. Lin Chaoxi took his campus card and swiped it through the door with a "beep".

Yongchuan University was almost on holiday, and there were few people in the library.

Lin Chaoxi shuttled between the bookshelves and quickly found the large row of bookshelves with school yearbooks according to the library's rules. She had already calculated the years when Old Lin might have enrolled and graduated, so she could directly pull out a few huge yearbooks and put them in Lu Zhihao's hands.

She took the remaining books herself and took Lu Zhihao to the long table by the window.

Several thick yearbooks were laid out in this way, and Lin Chaoxi turned them all to the page about the Department of Mathematics.

Under the scorching sun, the handwriting was densely packed, falling on the pages like grains of rice.

"Department of Mathematics, what are you looking for? I can help you." Lu Zhihao asked curiously.

"No need." Lin Chaoxi replied calmly and began to search.

From the list of incoming freshmen to the list of graduates...

She looked at the names one by one. These names represented the proud students of the old generation of the mathematics department of Yongchuan University. Lin Chaoxi had seen some of these names in textbooks later, so she felt particularly familiar with them.

Page after page, year after year...

Lin Chaoxi couldn't explain what he was expecting.

But she clearly remembered that after Lao Lin met her at Cheese World, he directly dialed the number that might belong to the Applied Mathematics Teaching and Research Section of Sanwei University.

He said two sentences, the first one was - "It's me."

The second paragraph was longer, but she could almost recite it completely. Lao Lin said: "A girl held my hand and said she was my daughter. We just came out of the appraisal center. I want to ask you, what is the probability of our relationship?"

The expression on Lao Lin's face at that time was still vivid in his mind. Lin Chaoxi had guessed more than once who Lao Lin would call after the father and daughter met.

But she couldn't seem to think of any other possibility except her mother.

If her mother is also a student at Yongchuan University, or a teacher, that seems to explain a lot of problems.

At that time, her thoughts were still somewhat sweet. A child like her who had grown up in love and care rarely had so many sinister thoughts. She thought that was a story that only happened in TV dramas.

At the same time, Lin Chaoxi finally saw the three words "Lin Zhaosheng" on the undergraduate admission list of the Department of Mathematics.

She breathed a sigh of relief and felt that the sunlight had softened, as it should be.

She gently closed the yearbook, as if everything had a natural explanation.

In fact, there are not so many so-called mysteries. The reason why she did not find Lao Lin's name in the Sanwei University yearbook is because Lao Lin studied at Yongchuan University.

She had been looking in the wrong place.

Doubts came and went quickly, and she suddenly had no doubts anymore.

The only thing she didn't understand was what Lao Lin meant by "dropping out of school".

So she opened the yearbook four years later and turned to the graduates column. As expected, she found Lao Lin's name again. Lao Lin was still an outstanding graduate that year.

I graduated from Yongchuan University. What's there to hide? I even wrote a story saying I "dropped out". It's a famous university after all...

Lin Chaoxi breathed a sigh of relief.

Now, she knew the school where Lao Lin graduated from, but she still didn't know who Lao Lin called.

At that time, she did not see the last two digits. If the phone numbers of various departments in a school were similar, she could not be completely sure that Lao Lin had called the Institute of Applied Mathematics.

So she ran back to the bookshelf, pulled out the Yongchuan University yearbook she had read when she was in fifth grade, and turned to the department phone number column.

She pointed at the numbers and scanned them from top to bottom, and began to check each phone number. The last four digits of the phone numbers of different departments and research institutes were different, which meant that the number 021-576323xx must belong to the Institute of Applied Mathematics.

Next up is the secondary office phone.

The phone numbers of the various departments under the Institute of Applied Mathematics are different, and the number 021-576323xx may belong to...

Institute Secretariat or Director's Office.

Lin Chaoxi was stunned and thought about it carefully.

Lao Lin said "it's me" very decisively. He didn't say "I'm looking for so-and-so" before that, which shows that he knew the person who answered the phone was the person he wanted to look for first.

Normally, there are different people on duty in the secretariat to answer the phone, so... could it be my mother?

As she thought this, she flipped through the catalog to find which page the list of institute staff was on.

Coincidentally, the school's major events of that year are located behind the catalog page.

Lin Chaoxi took a quick glance and found what she was looking for.

On x month x day of xx, the National Yongchuan University held a cadre and faculty meeting to announce the appointment and removal decisions: Comrade Su Anzhi was appointed as the director of the Department of Psychology and secretary of the Party Committee of Yongchuan University; Comrade Feng Deming was appointed as the director of the Institute of Applied Mathematics of Yongchuan University.

The records were made long ago, and printed on the brittle and yellow yearbook, they looked insignificant, but Lin Chaoxi felt an inexplicable shudder in his heart.

The director of the institute is what Lao Wang calls "Feng Taidou". Recently, he and Professor Zeng have been having some problems over the same diagram.

By the way, she and Professor Feng had met before. When she was in junior high school, Professor Feng was very vocal in opposing the popularization of Olympic Mathematics and attended a teaching seminar. She and Pei Zhi were invited to attend the seminar as students of the Olympic Mathematics Summer Camp.

At that seminar, Pei Zhi stood up and opposed the views supported by Professor Feng.

Like Pei Zhi, she did not like Professor Feng's views, but that was because she was a vested interest in Olympiad education.

From another perspective, she could actually understand and accept Professor Feng's views on the Mathematical Olympiad.

Lin Chaoxi frowned, thinking that he was thinking too far ahead. Why did Lao Lin, who knew him, call the director of a research institute?

The Secretariat is more likely.

She took out a pen and paper from her bag, wrote down the list of secretariat members, and closed the yearbook.

Lu Zhihao: "Are you okay?"

"Almost done." Lin Chaoxi stuffed the paper into his pocket.

If she wanted to know who her mother was, she could just tell Lao Lin her name and observe his expression to find out the answer.

But does this really make sense?

My mother worked at Yongchuan University for so many years, and she lived only a few hours’ drive away from her, but she had never come to see her. So what if she knew her name?

At most, when I have an argument with Lao Lin in the future, I will have a tool to counter him?

It seems like it really doesn't make any sense.

Lin Chaoxi felt empty and bored. The excitement she had just felt was gone. She put away the yearbooks on the table one by one, and together with Lu Zhihao, she stuffed the huge yearbooks back into the bookshelf.

"Why were you so excited all of a sudden? What are you looking for?"

"Find the answer to the mystery of my origins!"

"Hiss" Lu Zhihao took a breath of cool air and asked, "What about now, is it untied?

"It's almost solved. My dad is a student in the mathematics department of Yongchuan University. My mom should be working here. Because of some reason, my mom didn't want me anymore, so my dad raised me alone."

She stood in front of the towering bookshelves at Yongchuan University and gave the answer calmly.

Lu Zhihao was silent for a while, and then he said, "Don't be sad, it's all in the past."

"Yeah." Lin Chaoxi prepared to turn around.

"Your father is actually my senior, from which grade?" Lu Zhihao changed his tone to try to make her happy.

Lin Zhaoxi smiled and said, "He graduated in 1991, so he should be from the 91st class?"

After she said this, she suddenly stopped where she was, turned around in disbelief, and looked up at the row of thick yearbooks.

In the Sanwei University Library, Lao Lin wrote notes on many mathematics-related books, and the books were published no later than 1994. This means that around that time, Lao Lin was still engaged in mathematics-related work.

There is a three-year time difference here. Could it be that Lao Lin also studied for a master's degree at Yongchuan University?

So the so-called "dropping out" could only have happened during his postgraduate studies?

Lin Chaoxi took a step forward and pulled out the 1991 yearbook. She put the book down on the ground, knelt down and opened it.

In 1991, the three words "Lin Zhaosheng" were indeed included in the list of new graduate students admitted to the Institute of Applied Mathematics of Yongchuan University.

Lin Chaoxi's hands were shaking a little.

She looked up at Lu Zhihao and said, "Help me get the 1994 edition!"

Lu Zhihao quickly took down the huge booklet: "What happened again?"

Lin Chaoxi was unable to answer this time, so she flipped through the thick yearbook and looked at the list of graduate students.

Once, twice...

After reading it for the third time, she was sure that Lao Lin's name was not on the list of graduates.

He did indeed "drop out" and he did not lie to her.

But school yearbooks don’t state why students dropped out.

You may be expelled for some reason, you may be unwell, you may fail the exam, or you may even have no money to pay tuition...

But Lin Chaoxi has the most appropriate answer in his heart.

At that time, Lao Lin had a relationship with an unknown girl from the Department of Mathematics at Yongchuan University. The girl didn't want her, so Lao Lin left the school to support her.

All the problems returned to the starting point. She was still a burden to Lao Lin, although Lao Lin never admitted it.

Lin Chaoxi was still kneeling on the cold ground. Although the sunlight outside the window was still shining brightly, she still felt very uncomfortable.

She took out her cell phone and sent a WeChat message to Lao Lin - Why did you drop out of school?

Lao Lin—guess?

Lin Chaoxi - Because you gave birth to a daughter out of wedlock and had to raise your young daughter, you chose to leave the university campus.

Lao Lin - No.

Lin Zhaoxi smiled helplessly, closed the book and stood up, ready to let this question go, just as a little secret she knew. Of course, she still had the list of the Academic Affairs Office in her pocket in case of emergency.

Just then, her pocket vibrated again.

Lin Chaoxi had no choice but to take out his phone again, and found that Lao Lin had actually sent a long text.

Lao Lin——1. During his defense at Yongchuan University, Lin Zhaoxi met a strange middle-aged man who suddenly came to you to claim to be his relative. a. Yes; b. No.

Lin Chaoxi was shocked and subconsciously wanted to ask what "recognizing relatives" meant or what a "strange middle-aged man" was. However, based on her many years of experience in fighting wits and courage with Lao Lin, if she raised any questions about Lao Lin's ambiguous words, Lao Lin could directly judge that she had not encountered the above situation.

So, she just hit it - a.

Lao Lin directly sent a voice message to Lin Chaoxi. Lin Chaoxi opened it and put it to his ear. Lao Lin's gentle voice with a hint of smile came out: "Congratulations to Comrade Lin Chaoxi for activating the hidden copy. You can make the following choices. a. Listen to the strange middle-aged man continue to beep. b. Turn around and leave without hesitation. Call your not-so-familiar good friend Lu Zhihao at Yongchuan University and ask him to borrow a campus card. Go to the archive room on the fifth floor of the university library to check the 1994 school yearbook and look through the disciplinary cases of graduate students in the Department of Mathematics that year. Piers, according to custom, it is around page 520.

After the voice message ended, Lin Chaoxi opened the yearbook in front of him in an almost unbelievable manner.

It doesn't even take a second.

It was on page 520, on the 1994 Mathematics Department disciplinary list, that she saw Lao Lin’s name.

——Lin Zhaosheng was expelled from the school because his master's thesis "Research on Theory and Method of Graph Isomorphism Verification" was suspected of academic plagiarism. After research and decision by the department's party committee, he was expelled from the school.

The author has something to say: Lao Lin, Lu Zhihao, Feng Taidou - Yongchuan University (Honorary Alumnus Comrade Lin Chen)

Lin Zhaoxi, Pei Zhi, Jie Ran, A Guang, Lao Wang - Sanwei University

chu——the school that Lao Lin and Pei Zhi are going to study abroad (a made-up name that is passed down from generation to generation)