"no!"

This time, the person who refused was Lao Lin.

They stood at the door of an old glutinous rice dumpling shop near the park, the plastic curtain swinging.

She was carrying a school bag, which now only reached Lao Lin's elbow. She looked up at the tall, thin and dark Lao Lin, then glanced at the Tangyuan shop: "Master, please treat your disciple to a meal, a feast for your apprenticeship."

"Little friend, let's sort out what happened." Old Lin stood with his hands behind his back. He suddenly calmed down and spoke slowly, more like the Old Lin she was familiar with.

"Master, please tell me."

"You only have to answer yes or no."

"Okay."

"You've been pestering me since we met."

Lin Chaoxi was about to explain herself, but Old Lin's cold eyes came over her, so she had no choice but to change her words and forcefully said, "Yes."

"You said you were pestering me because I was good at fast calculations and you must know math, so you wanted me to be your teacher and let me teach you math."

"yes."

"But I didn't promise to teach you math."

"yes."

“So I am not your master at all.”

"……yes."

"Then there is no such thing as a teacher appreciation banquet, and I don't need to treat you to a meal."

“…”

Is your point that you don't want to spend money to treat me to a meal? Lin Chaoxi slapped her face and almost laughed. She naturally took Lao Lin's arm and sat down on the steps without going into the store.

Lao Lin was very reluctant, but he really couldn't stand her, so he sat on the ground with difficulty, unable to stretch his legs.

"Master."

"I am not your master."

"uncle."

"I'm not your uncle."

"dad."

“…”

Lao Lin said nothing and took out another cigarette.

The street lights were gradually turning on, but the sky was not too dark, and it was still hazy. Lin Chaoxi could not understand his expression at this moment, and she felt that it was too rash to call him dad, but she had been used to joking with Lao Lin for so many years, and it was too difficult to change it suddenly.

She took the schoolbag, pulled out the Mathematical Olympiad exercise book, and turned to a page with questions folded in the corner. Using the light from the sky and the light from the store, she pointed to the question with a five-star difficulty rating and asked Lao Lin, "I don't know how to do this question. Can you teach me?"

Lao Lin didn't even look at him, but said calmly: "Tell me, why are you pestering me?"

“I want to study mathematics.”

"Tell me the truth."

"I have the Mathematical Olympiad exam next week, which is the summer camp selection for Jinbei... If I don't pass it..." she drawled.

"Don't keep me in suspense when telling the story. I'm not really interested in it anyway."

"Summer camp is my last chance. If I fail the entrance exam, I can only go to Red Star Middle School according to my location. The school is too bad. My life will be over... So I want to go to summer camp and then be recommended to the Zhongshu class of Experimental Middle School, the best class in the city."

"You missed something?"

"ah?"

“Only the provincial champions can be admitted to the Zhongshuban class without taking an entrance exam, but the mathematics education in primary schools in Anning has always been rubbish.”

"Wow, you even know this! You just answered such a difficult question in one go, especially the 'Sweeping Monk' in Demi-Gods and Semi-Devils. The 'Sweeping Monk' is very powerful." Lin Zhaoxi pretended to be stupid and secretly explained the reason why she was pestering Lao Lin.

Old Lin looked like he was saying "damn it, you've said too much again", but he didn't suspect anything.

Because he had no suspicion, he patted his butt, stood up, put the cigarette in his mouth, and left as if he didn't know her at all.

Lin Chaoxi looked at her father's back and knew that Old Lin was determined. He was willing to talk to her before, but he didn't understand why a loli like her would act so violently in front of him.

Now that I know the reason, it's still such a boring one, so of course I have to leave.

The sky was getting darker and darker, and Lin Chaoxi knew it was time for him to go back.

"Master, do you live at No. 284, Zhuanzhu Lane?" Lin Chaoxi shouted as the noisy sound of cars rolling over the road was heard everywhere.

Lao Lin turned around suddenly, his face full of shock.

Lin Chaoxi already knew the answer.

Her birthday is February 20th, and 220 and 284 are a pair of amicable numbers. This is the fundamental reason why Lao Lin must rent that house. It is the romance of a mathematician.

She jumped up with her schoolbag on her back, waved the Mathematical Olympiad exercise book in her hand, and shouted, "See you tomorrow."

Then, without giving Lao Lin a chance to turn around and catch her, she turned around and ran in the opposite direction.

The glow of the distant city fades, the starlight gradually rises, and everything will be fine.

Lin Chaoxi thought.

…

Early in the morning, to be specific, at seven in the morning, brisk footsteps stepped on the bluestone slabs, and the sound of footsteps echoed in the alley.

Most of the people living in the alley are elderly people. They get up early to buy vegetables and light the coal stove. The alley is full of the smell of coal smoke.

Lin Chaoxi stood in front of No. 284 Zhuanzhu Lane, sneezed, and started banging on the door.

Boom boom boom.

"Master, wake up!"

Boom boom boom.

"I'm here to serve you!"

Boom boom boom.

"Open the door!"

There was no response from the iron door, which was within Lin Chaoxi's expectations. Every time she knocked, she would stick to the window to see if there was any movement in the room. In the dim window shadow, the person on the bed was still covered with a blanket, sleeping soundly, and was not woken up at all.

The hardest person to wake up is someone who is pretending to be asleep. She was not in a hurry. She walked to the door again with low steps. When she was about to knock on the door, someone behind her suddenly said in a sinister voice: "Get lost..."

"Wow!" Lin Chaoxi was shocked.

Sure enough, Lao Lin opened the window a little and stood by it. His face was dark and wrinkled, and his expression was so gloomy that water seemed to drip from it.

Lin Zhaoxi quickly turned around and smiled, "Master, you're awake."

"no."

"Then could you please open the door for me and continue sleeping?"

Old Lin had a blank expression on his face and a hollow look in his eyes. He turned around mechanically and covered his chest. Lin Chaoxi shamelessly approached and stuck her hand in the window, but Old Lin was so sleepy that he didn't see her movements at all. He numbly walked to the bed and covered his head with a blanket.

Lin Chaoxi wanted to open the window little by little, but when he pulled it for the first time, a shrill "creaky" sound slowly echoed back.

On the wooden bed, Lao Lin twitched violently.

"I'm sorry, I'm sorry." Lin Zhaoxi apologized quickly.

I don’t know what kind of magic this “I’m sorry” has. It was clearly a very gentle voice, but the Chihuahua next door suddenly let out a startled “Woof!”

Lin Chaoxi was a little curious and shouted again: "I'm sorry?"

"Woof!" A loud noise.

"right……"

Lao Lin couldn't stand it anymore, he kicked his legs and turned over to sit up: "Come in, come in, come in!"

After saying that, he slammed the door, entered the yard, and opened the gate like a gust of wind. When Lin Chaoxi stuck his head out, he was dragged into the yard by the ear.

Lin Chaoxi didn't have time to cry out in pain. All he could see were overgrown weeds and chaotic rocks. He could only vaguely see a small path made of red bricks connecting the kitchen and the two bungalows where he slept. The well in the yard had not changed, and it was completely different from the small yard full of life in his memory. The ground was piled with beer bottles and messy cigarette butts, leaving him with nowhere to step.

Lin Chaoxi stood there in a daze for a while. She looked up at the sky. The sunlight shone through the grape vines, and the leaves underneath had turned yellow.

This was her first time going home after becoming a child. When she was at the door, she had many beautiful fantasies in her mind, so she was very excited whether knocking on the door or waking Lao Lin up. But when she saw the real situation inside, she felt like she was poured with a basin of cold water and felt very uncomfortable.

Lao Lin pointed to the kitchen and said three words: "Didn't you say you would serve me? Go and make breakfast."

Then he put on his slippers and went back to bed.

Lin Chaoxi didn't react for a moment. When he came to his senses, Old Lin had already locked the bedroom door.

She originally wanted to take care of Lao Lin, but she had no choice but to go into the kitchen. A minute later, she had to come out again, walked to Lao Lin's door, and knocked timidly: "Master... Mi... Where is Mi?"

There was a loud thud, as if Lao Lin had hit his head against the bed rail.

Lin Chaoxi also felt guilty. She took a few steps back and wanted to run away quickly.

But thinking about it, she stepped back and whispered, "Actually, I didn't find the pot either..."

In an instant, the door opened, and Lao Lin rushed out of the room and into the kitchen without saying a word. He took out rice and pots, turned on the gas stove, started to light a fire and cook, and shouted: "I did it myself, I did it myself, can you leave!"

Lao Lin had already broken down and really started to make breakfast seriously.

"No, Master." Lin Zhaoxi looked at his father busy in the kitchen from a distance, stood on tiptoe and said, "I haven't had breakfast yet, I'm so hungry."

After that, she moved a small chair and supervised at the door of the kitchen. When the porridge was almost ready, she tidied the small stone table under the grape trellis and instructed Lao Lin to put the porridge and salted vegetables on the stone table. Then she went in to wash the dishes and chopsticks. When she took them out, Lao Lin was sitting under the grape trellis, smoking and looking at her.

She stopped calling him master and served herself two bowls of hot porridge.

"How do you know I live at No. 284 Zhuanzhu Lane?" Lao Lin suddenly asked when she was almost finishing her porridge.

Lin Chaoxi held the tip of his chopsticks in his mouth, took the last sip, looked around and said mysteriously to Old Lin: "284 is a good number, Master."

"Haha." Lao Lin blew out a smoke ring, "What should I do?"

"The number 284 is 2 raised to the first power, the third power, the fourth power..."

"Is cube taught in primary school?"

"Master, I am good at self-study." Lin Chaoxi smiled at Lao Lin, very proud.

"Anything else?" Lao Lin asked again.

"And... the combination of 284 and another number once played an important role in the history of number theory." She said, observing the expression on Lao Lin's face and asked, "What is the other number, Master?"

There was no expression on Lao Lin's dark face. When he heard this question, he smiled and said, "How should I know?"

"Then I'll tell you!" Lin Zhaoxi shook his chopsticks like a kid showing off his knowledge: "Pythagoras once said, 'Friends are the shadows of your soul, as close as 220 and 284.'"

"Intimate?"

"Intimate means that, excluding 220 and 284 themselves, the sum of all their divisors is equal to the other. In short, although our two numbers look completely different on the surface, they constitute each other internally, so many relatives and friends like to use these two numbers to express their thoughts, love, etc."

Lin Chaoxi finished his words in one breath, then paused and asked Lao Lin tentatively, "Master, are you living here to commemorate someone?"

Old Lin blew out a puff of smoke, his eyes and eyebrows were obscured by the smoke, so it was hard to see clearly. Just when Lin Chaoxi thought he was going to reveal his true feelings, he heard him ask sharply: "But my question is, how did you know I live here?"

Lin Chaoxi put down her chopsticks, sighed, and felt a little regretful. She said to Lao Lin earnestly, "Master, I'm not stupid. If I tell you, you will chase me away again." Lin Chaoxi smiled, "Remember to open the door for me tomorrow. I'll tell you or not."

Lao Lin also laughed: "Do you think I'm stupid?"

"Of course I'm not stupid." Lin Zhaoxi shook his head: "Master is..."

She originally wanted to say that the master was the smartest person in the world, but before she could finish her words, Lao Lin came over, lifted her up from the ground with his hands, and then...

He threw the person and his schoolbag out of the door.

The door panel fell on his nose, Lin Chaoxi patted his butt and stood up, nothing happened.

She put on her schoolbag, straightened her red scarf, and pretended to be out of the house, on her way to school. What she couldn't tell Lao Lin was that she was actually closely related to 220, but because she was abandoned, the welfare home didn't know her date of birth, so they all said April 1st was their birthday, which was neat and easy to remember.

The author has something to say:

The sum of all the true factors of 220 (1, 2, 4, 5, 10, 11, 20, 22, 44, 55, 110) is 284; and the sum of all the true factors of 284 (1, 2, 4, 71, 142) is exactly 220.