Xueba, I beg you to go and escort him quickly!

Just like he did to the boss!

Lao Yao's scalp was even numb.

"Okay! It's nothing, I'll go back first!"

"By the way, play less on your phone and go to bed early, bye."

Passing by Lao Yao, the principal reminded, "Don't worry about this classmate's cell phone..."

Lao Yao, "Yes, yes, yes! Mr. Principal, do you have anything else to say?"

The principal smiled, "It's nothing! Don't be so nervous, I just came to Xu Heng's dormitory to pick up my umbrella, nothing else!"

I made a special trip to Xu Heng's dormitory to get my own umbrella!

!!!

Come on!

Lao Yao saw it with his own eyes!

"hiss……!"

Looking at the back of the principal leaving, he looked at Xu Heng's dormitory.

The more he is afraid!

If there was really a big trouble yesterday, if you don't say it yourself, I'm afraid you'll even implicate the boss.

"This is an ancestor! In the future, we must make a sacrifice."

Xu Heng's dormitory.

After the principal left, the roommates dared to breathe loudly.

Xu Heng rolled his eyes, "You shouldn't be like this! The principal is also a human! You are also human! What are you afraid of!"

Everyone pouted, "Xu Heng, be yourself! Not everyone is like you!"

Xu Heng waved his hand, "Damn! Just continue to be afraid, I'm going to sleep! Huh..."

Just about to turn around, Yang Kaixuan leaned over.

"Xu Heng, tell me about this question!"

"This is from Hong Lao who came out of the group, and he also gave a way to solve the problem, but I think there should be a second way to solve this problem!"

"Look first, I'll go wash up."

Xu Heng looked at the question.

求所有自然数n，使得min/k∈N（k2+[n/k2]）=1991，这里[n/k2]表示不超过n/k2的最大整数1991。

It is worthy of being a question posed by Hong Lao, which is innovative and difficult.

but--

Xu Heng called Yang Kaixuan to stop, "Come back, I'll talk to you first, after I'm done, go wash up!"

Yang Kaixuan, "???!!!"

"Xu Heng, what did you say?"

"This question, do you know how to do it?"

"My God! You can't spy on the screen!"

Xu Heng, "%￥#@￥..."

Yang Kaixuan, "I'm talking about a brand new idea, not the one Hong Lao said."

Xu Heng sighed, "Then please tell me, which one is Honglao talking about? I won't use that one."

clap la la...

As soon as this word comes out!

Yang Kaixuan is determined to die!

"This, this, how is this possible! After you saw this question again, there were more than two ways to solve the problem in your mind immediately?"

"???"

"Xu Heng! You are simply not human!"

Goosebumps from head to toe.

Although Yang Kaixuan knew that Xu Heng was very strong, unbelievably strong, he was still shocked!

How to do?

Just so strong!

Yang Kaixuan thought he was immune!

However, his body's reaction told him that he didn't!

Even watching Xu Heng answer questions in seconds, he couldn't believe it and was shocked.

"This question, Honglao gave us half a day, before someone managed to solve it!"

"And it was made by the seniors of Peking University!"

"hiss……"

"Xu Heng, are you sure?"

Xu Heng rolled his eyes at Yang Kaixuan, "Don't listen? It's fine if you don't want to listen, I'm going to sleep..."

Yang Kaixuan's attitude changed immediately, "Don't, don't, don't! I'll tell you Honglao's thinking first, and then I'll listen to yours."

"Teacher Hong according to..."

It's only half of it, no, it's a third of the idea.

Xu Heng interrupted Yang Kaixuan's words and spoke directly.

And picked up a pen and paper and wrote it out.

solution:

According to the conditions, it is equivalent to, for all k∈N, k2+n/k2≥1991... (1)

And there exists k∈N, making k2+n/k2<1992...(2)

（1）等价于对一切k∈N，k－1991k2＋n≥0即（k2－1991/2）2＋n－19912/4≥0……（3）

because……

故（3）式左边在k取32时最小，因此（1）等价于n≥1991× －32＝1024×967

又，（2）等价于存在k∈N，使（k2－996）2＋n－9962＜0

上式左边也在k＝32时最小，故（2）等价于n＜1992× －32＝1024×968

故n为满足1024×967≤n≤1024×967＋1023的一切整数．

Finished.

Not even 2 minutes!

Xu Heng gave the pen and paper to Yang Kaixuan, and he turned over and fell asleep.

Only Yang Kaixuan was left standing in front of his eyes, dumbfounded.

This question made the whole group cry and scream.

But in Xu Heng's hands, he didn't survive for 2 minutes!

Do not!

To be more precise, in Xu Heng's hands, that is, during the time of reading the question, there is still time to struggle with this question.

As long as the question is finished, this question is no different from "the fish on the sword", and Xu Heng can do whatever he wants to do, it will be completely finished!

"so horrible!"

After Yang Kaixuan looked at Xu Heng's problem-solving ideas, he spent half an hour digesting it, and then sent the photo written by Xu Heng to the group.

The group exploded in an instant, "Xu Heng's handwriting!"

"Xu Heng made it big? It's completely different from Honglao's thinking!"

"My God! How did you make sure that this is Xu Hengda's handwriting?"

"Beautiful! It looks like calligraphy, no doubt it's Xu Heng!"

"Please give me a gift! @杨凯轩! Please give me a gift! I'll give you the address, pay on delivery! This is too beautiful!"

Yang Kaixuan, "%￥#@￥#..."

"Everyone, are you going astray! Let's discuss this question, shall we?"

"Also, let's guess how long it took Xu Heng to come up with this problem? No, to be more precise, how much time did it take to come up with different ways of solving this problem? of?"

This question is more difficult!

It has already made everyone feel the malice of the question maker.

It was just a way of solving problems before, and it took them half a day.

"This question is so difficult, it is also difficult for Xu Heng!"

"Although Xu Heng is a special alternative! Maybe he can think of the first way to solve the problem, but the second way must take a long time."

"I agree with the student above, I think Xu Heng needs at least four or five hours!"

"I think it will be within 3 hours!"

"Is there any less?"

"2 and a half hours?! I think 2 and a half hours is the limit!"

"Xu Heng's problem-solving idea is very ingenious! I think it will take a little longer."

The group leader, "@杨凯轩, don't be a fool, so Mr. Xu Heng, how much time did it take?"

Yang Kaixuan, "1 second!"

"After reading the question, Mr. Xu Heng gave the corresponding answer."

moment!

The group is silent!

group, there will be no second message.

Yang Kaixuan, "I didn't lie to you! Really! He is just a second!"

After a while, someone said, "Fuck, blah, blah, blah, blah..."

"Fuck, fuck, fuck..."

"Xu Heng is very powerful and domineering!"

"Xu Heng is awesome!"

"Xu Heng, I am a god!"

But some people questioned, "One second? Impossible! This, this... Even if he can know the answer in one second, I don't believe that he can know two ways to solve the problem at the same time?"

Yang Kaixuan, "I can understand what you mean, but... this classmate, what I want to correct you is that Xu Heng probably knew more than one way to solve the problem at the first time."

"For example, this question is like an egg, and doing this question is like frying vegetables with eggs."

"When Xu Heng picked up the eggs, he was thinking about scrambled eggs with tomatoes? Scrambled eggs with green peppers? Scrambled eggs with carrots? Stewed eggs..."

"These scrambled egg methods are his problem-solving ideas!"

"I'm right next to him! Seriously! Every time, I thought I wouldn't be shocked or get goosebumps, but I'm always disappointed."

"Hey……"

The last sigh was Yang Kaixuan's helplessness.

Although it was posted in the group, everyone could see the despair that Xu Heng brought to Yang Kaixuan.

Everyone, "%￥#@@￥￥......"