[Chapter 40, Prime Maze 02]

At 8:00 in the morning, the examination room for the compulsory course "Prime Number Labyrinth" of the School of Mathematics opened.

The four of Yue Xingwen were instantly pulled into a strange maze. The room of the labyrinth is a cube structure. The upper and lower, front and rear, left and right, the six walls are painted with special black paint, and there are many star-like embellishments, just like being in a dark, deep universe. In the middle, those "stars" emit a faint light, illuminating the room.

There is a door on each of the four walls, and four digital cards are pasted on the door with white fluorescent characters. The cards are shiny, just like the score cards of the "Orienteering" course, which can be taken down. collect.

Additional Question: Collect all twin primes.

They should take down all the "twin primes" cards posted on the wall to complete the extra questions.

Yue Xingwen's eyes quickly looked around, and the four numbers in the first room were very simple, 4, 5, 6, and 7.

The prime numbers of the one digit are easy to find, and 5 and 7 are a pair of twin prime numbers. If you get the wrong card, the additional questions will definitely not be given points, so, first, you must calculate it clearly before taking the card.

Yue Xingwen looked at Jiang Pingce: "The 3-credit labyrinth course, shouldn't it be too simple?"

Jiang Pingce frowned and thought for a few seconds, then said: "There are 4 doors in each room. If there is a passage behind each door, then the number of doors in this maze is 4 to the nth power. The difficulty is not to find the twin primes, but to find the right path. We need to walk the maze, draw while drawing, and judge the direction clearly.”

Ke Shao Bin quickly took out his laptop: "I can write a piece of code to quickly figure out which prime numbers are, and build a maze model by the way... Wait, my laptop doesn't seem to be able to open. machine?"

Liu Zhaoqing leaned over to take a look: "No? Is it broken?"

Ke Shao Bin put his fingerprint on the power button and pressed it for a long time. He asked in confusion, "Don't you allow the computer to be used?"

Yue Xingwen helped his forehead helplessly: "It seems that this test cannot be calculated by computer, we have to calculate it ourselves." He raised his head and glanced at the countdown in the upper right corner: "The test time is 4 hours, and the road is fork in the road. If there are too many? It should be too late for us to investigate slowly?"

Liu Zhaoqing spread his hands and said, "I haven't touched mathematics for many years. Let me do division, and my mind is a mess. In this course, you can treat me as a mobile pendant, and I will follow it quietly. behind you."

Yue Xingwen smiled and said, "I'm about the same."

Jiang Pingce suddenly said solemnly: "In order to clear the customs in the fastest time, we still explore the way in teams."

Ke Shaobin and Liu Zhaoqing looked at each other and said in unison, "Team?!"

He must be teaming up with Yue Xingwen, can the other two do it?

Ke Shao Bin was embarrassed to hold his glasses and his ears turned slightly red: "Although I am a science student, I have been accustomed to using computers to solve all calculation problems since my freshman year. It's been a long time since I did math by myself. For multiplication and division with more than three digits, I have to do it several times with pen and paper to understand it. Brother Liu and I are in a team, so the efficiency might be very low, right?"

Jiang Pingce said: "It's not divided into two teams."

He turned his head to look at the teammates beside him, and said word by word, "It's divided into four teams, each one on a team."

Three people: "..."

are you joking? Liu Zhaoqing looked terrified: "I'm really bad at math!"

Yue Xingwen quickly understood his thinking: "What do you mean, four of us are going to explore the road separately, and the calculation tasks are all handed over to you? You alone can calculate the prime numbers of four roads at the same time. ?!"

Sure enough, Xingwen knew him better, Jiang Pingce nodded calmly.

Ke Shao Bin and Liu Zhaoqing stared at him with wide eyes.

I thought that the team he said was divided into two teams, but as a result, Jiang Pingce was more ruthless than everyone imagined - directly divided into four teams! He counts four roads at the same time by himself!

Obviously, he has enough confidence in his computing power.

Jiang Pingce looked at Yue Xingwen and said seriously: "The research group channel can send messages during the exam. Every time you enter a labyrinth room, type the number on the door on the research group channel. come up with the correct answer."

Yue Xingwen tried to post a line on the research group channel: "Can you see it?"

All four people saw the information in the transparent floating frame in the upper left corner.

Yue Xingwen's eyes lit up: "This method is amazing! The four people are divided into four paths to go forward, which can greatly save the time of exploring the maze, and the number of wrong paths back and forth will be reduced." He paused, and looked at Jiang Pingce with some worry, "But in this case, you will be under a lot of pressure, right? There are four roads, and in case of confusion at the back, can you tell the direction clearly? ?"

If Jiang Pingce's judgment is correct, there are four doors and four paths in each labyrinth room, then the correct path has as many as 4 to the nth power, and the path increases exponentially. Can he remember?

Jiang Pingce looked at Yue Xingwen, his dark eyes bright? His pupils were full of seriousness: "Trust me."

When he met his gaze, Yue Xingwen immediately nodded: "Okay, I believe you, just do as you say!"

Jiang Pingce said: "First, take out your dictionary, tear some paper and give it to me, and I will draw a map of the maze path."

Yue Xingwen did as he did, and took out a pen from his pocket and handed it to Jiang Pingce.

Jiang Pingce walked to the wall with the number [5] pasted, opened the door, and the next room was exactly the same as this room, and it also had four walls with four stickers on it. number.

Jiang Pingce tried to open the other three doors [4] [6] [7] again, and came to the same conclusion.

Prove his reasoning - each room has four doors and four exits. Some of the rooms in the back are sure to turn into dead ends. If you want to find the correct exit of the maze, if the four of them are together, and they slowly check the rooms one by one, of course they can walk out in 4 hours. However, if they want to get it in this course High score, certainly can not use this most stupid method.

Jiang Pingce quickly drew a few squares on the paper and explained: "Everyone, you have traveled a lot, and you can't remember the direction. For example, the current room has four numbers 4, 5, 6, and 7. After opening the door with [5] written on it, you will enter the next room, and remember the number of the other door connected to [5]. When reporting the number, Just start from the door you walked in, count clockwise, see what I mean?"

Yue Xingwen saw him draw five consecutive rooms on the paper, all square, with a number on each side. As he said, there are more than one path behind, and the sense of direction becomes a floating cloud. The east, west, north and south must be indistinguishable. What's more, all the walls in this maze have been painted into starry sky.

If you want to locate the exact direction, you must use the room of the previous maze.

For example, the door directly in front of room a is marked with [5], which is regarded as [door number 5]. After opening this door, it is room b. Since room b is also a square, two squares will be connected together. Sharing one side, that is, the four walls of room b, there must be a door directly connected to [door 5] of room a.

The logic used by Jiang Pingce is "two rooms share a door, with different numbers on the front and back of the door". Then, starting from the first room and continuing to reason down, you can deduce a complete maze graph.

This kind of reasoning method does not need to care about east, west, north and south, as long as every room is correct, his diagram will not be wrong.

Jiang Pingce looked at the three teammates and warned again: "First, you must remember the number on the door that you pushed open, and immediately look at the number on the back of the same door after entering the next room. , report the number clockwise, don't report errors. If you make one mistake, there will be a series of mistakes later, everyone? Do you understand?"

The three looked at each other and nodded in unison, "Understood!"

They can't tell the difference between east, west, north and south, and they can still tell the difference between clockwise and counterclockwise!

Jiang Pingce said: "Prepare for a team. Ke Shao? Go to Gate 4, I'll go to Gate 5, Xingwen 6, Liu Senior Brother 7."

Yue Xingwen took the initiative to reach out: "Come on, let's cheer for Xueba."

Liu Zhaoqing and Ke Shaobin put their hands up consciously, Jiang Pingce glanced at Yue Xingwen, and put his hands up in cooperation, Yue Xingwen gently covered his with the other hand. On the back of his hand, a bright smile: "Come on, don't put too much pressure on yourself, we can pass the test, there's no need to rush for the first place, you know?"

Jiang Pingce felt warm in his heart and nodded at him: "Well, everyone? Don't take the wrong card. The standard for scoring additional questions must be that all the cards we collect must be twin prime numbers, and points will be deducted if you take the wrong one."

The four people looked at each other, walked into the four doors separately, and the number appeared again in the next room.

This time it's double digits.

Yue Xingwen's room is 11, 12, 13, 14; Ke Shaobin's room is 16, 17, 18, 19, Liu Zhaoqing is 28, 29, 30, 31, Jiang Pingce is 40, 41, 42, 43.

The two-digit number is very simple, and everyone can calculate it by themselves, but for the convenience of Jiang Pingce's drawing, the three of them still follow the rules he said and start counting clockwise from the door they entered.

Jiang Pingce instructed: "Take off the twin prime number card, Xingwen goes 13, Ke Shao? 18, Senior Brother 30."

All he chooses is the road in front of him. First, he walks in a straight line. When he encounters a dead end, he retreats to the right, and then to the left. This way, there will be no confusion.

The four quickly entered the next room, this time with three digits.

Jiang Pingce: "Brother take 107 and 109 and go through the door of 111."

According to his instructions, Zhaoqing took down two number cards and moved on.

The research group channel kept popping up messages from Jiang Pingce: "Xingwen takes 137, 139, and goes to 133."

"Master Ke? Take 179, 181, and go to door 181."

In the next room, the prime numbers become four digits again.

Two-digit and three-digit numbers can still be counted, but after reaching four-digit numbers, the three of them simply gave up thinking. If they had time to do the math on their own, it would be better to type quickly. Wait for the result of Jiang Pingce.

Jiang Pingce's brain speed is astonishing, and he can even give an answer in seconds by calculating four paths at the same time!

"4019, 4021" "8969, 8971" "9281, 9283..."

Walk one more room, and the number rises to five.

"16829, 16831" "31541, 31543..."

But for Jiang Pingce, five-digit numbers were not difficult, and he quickly and accurately reported a pair of twin prime numbers.

Teammates collect more and more prime cards in their hands. Jiang Pingce not only has to calculate the twin prime numbers of the four roads at the same time, but also draws a maze path while walking to ensure that the direction of his teammates is correct...

In this labyrinth full of numbers, other people's eyes are smeared, and they don't know how to walk, but Jiang Pingce is like a duck to water-these numbers are his closest friends since childhood. When he was in high school, he participated in the national mathematics competition. He liked mathematics from the bottom of his heart, and liked the wonderful, rich and rigorous world made up of numbers.

In the world of mathematics, he is like a natural king. Others are afraid of numbers, but he can control them.

The numbers in the room are getting more and more complex, and the amount of calculation is increasing like crazy.

Jiang Pingce is like a high-speed computing machine. As he calculates, he gradually draws a maze in his mind. As soon as his teammates type the numbers, he can always give the correct answer the first time. .

Yue Xingwen: "The front room is a dead end, and there is no door."

Jiang Pingce instructed: "Go back one room and go to door 8861."

Ke Shao Bin quickly said, "I have encountered a dead end."

Jiang Pingce: "Go back and go to gate 9657."

"Brother come back, door 9861."

Under the command of Jiang Pingce, everyone went back and forth to explore the road, and the number of forks in the entire mathematical maze was almost innumerable. Yue Xingwen alone took eight forks. It is hard to imagine that Jiang Pingce did not go wrong.

I thought that if they continued to investigate like this, they would soon be able to check all the fork in the road. However, when the number of twin prime cards collected by Yue Xingwen reached 30, the research group channel suddenly appeared? A message from Liu Zhaoqing: "Come on, there is an elevator in the room I entered, and there are up and down buttons."

After a few seconds, Ke Shao Bin also sent a message: "I entered the door of 24189, and there is also an elevator inside."

Liftable elevator?

Yue Xingwen said, "Could it be that this maze has at least three floors?"

Jiang Pingce said: "I expected it a long time ago. The course description says that this is a three-dimensional maze. No matter how many roads there are in a plane maze, it is not difficult to make marks and explore slowly, and the difficulty of the three-dimensional maze will be doubled."

Yue Xingwen worried: "Three-dimensional maze, your calculation amount will also be doubled, right?"

Jiang Pingce said: "It's okay, go back first, let's collect the twin prime numbers on this floor before going upstairs."

Want to do extras and collect all the twin primes, that means they have to explore all the rooms in the maze.The three were already confused and could not tell the difference between north and south, but Jiang Pingce's calm and clear command gave them full confidence.

In this vast digital maze like a starry sky, not only should four lines be calculated at the same time, so that teammates can quickly find the twin prime numbers in the dense numbers, but also ensure that in the process of repeatedly pushing the door, exploring the way, and returning, do not let theTeammates are lost.

With such a difficult command, other teams may not even dare to think about it.

But Yue Xingwen believed that Jiang Pingce would definitely be able to do it.w, please keep in mind:,