A simple geographical idea:

First of all, the second puzzle, literally, Lan Silin wants him to find someone - that is, in that person, there must be the answer to the puzzle, or the existence of a third letter.

Second, we need to take into account the problem of information symmetry. Lan Silin let herself find the betrayer, but the betrayer himself should not have known that he was being targeted - he should have just been entrusted by Lan Silin to keep a letter for himself.

In this form of reserved puzzles, since Lan Silin himself had left Kanglong Academy, he could never make any adjustments to the unexpected situation, and he had no way of knowing the process of Li Weiyin's puzzle solving, so Li Weiyin could forcibly solve the puzzle in a way that did not conform to the rules of the game.

- There is no need to find the "betrayer", as long as the scope is determined.

Then, ask one by one.

Don't worry about startling the snake, because in the entire Kanglong Academy, except for himself and Lan Silin, no one knows what they are doing.

Although such a method is not very glamorous, for Li Weiyin, as long as the result is correct, it does not matter what the process is.

Once you've figured out the middle joint, it's time to put it into practice.

During the lunch break, Fan Lei cooked as usual and prepared to go to the table at Fang Chang's end. When he turned around, he ran into Li Weiyin who was holding a lunch box.

Li Weiyin's face was expressionless, and he asked:

"Do you have a letter from Lan Silin?"

He subconsciously opened his mouth, revealing a look of surprise.

"It's you?"

Li Weiyin's brow furrowed. Before he could speak, Fan Lei looked left and right nervously, noticed that the instructor did not look here, and whispered:

"Follow me."

The two put down their lunch boxes and walked to the door of the dining hall as if nothing had happened, without attracting anyone's attention.

went downstairs, Fan Lei ran straight to the playground, Li Weiyin followed, the two went all the way back to the playground, there were students playing football on the playground, Fan Lei breathed a sigh of relief, slowed down, and walked to the other end of the sand pool.

"Lan Silin only told me that about a week after he left school, someone would come and ask me for a letter. I didn't expect that person to be you, nor did I expect it to be so fast. ”

Li Weiyin didn't speak, he had his own considerations in his heart - Lan Silin was not omniscient and omnipotent, he reserved a week for himself to solve the first two puzzles, but he didn't expect that he had come this far only the day after receiving the puzzle.

The man underestimated himself.

Thinking of this, Li Weiyin's heart settled down a little, and he asked:

"Do you know what he's trying to do?"

"No one in the entire Kanglong will know what Lan Silin wants to do." Fan Lei smiled bitterly and shook his head:

"He's a complete lunatic."

"One day, about a month ago, I had just eaten dinner and was about to take a shower, when he stopped me downstairs and asked me to walk with him for a while. On the way to the playground, he told me all about my life history, even some personal things that I never told anyone......"

Li Weiyin was stunned. A strange thought arose in my heart.

How many letters did Lan Silin leave behind? Are you just a cog in his chain layout?

"He threatens you with this?"

"In this kind of place where you can't see the light of day, even if you know that there is a mole under my **, it can't threaten me." Fan Lei smiled self-deprecatingly:

"In order for me to keep an eye on the letter and wait for the next person to pick it up, he gave me a condition...... A condition that I couldn't refuse. ”

"On what terms?"

"He promised to arrange for my family to pick me up within a month of his departure."

Li Weiyin narrowed his eyes: "You just believe him like that?" ”

"There's no reason why I shouldn't try." Fan Lei is obviously also a relatively upright character, he shrugged:

"All I have to do is keep a letter and give it to the next person. There is no risk or effort involved. Besides, since he has the ability to go out and knows so much about my private affairs, it must not be difficult to contact my family, I should always try. ”

Li Weiyin acquiesced to this statement in his heart, Fan Lei is indeed a very smart person.

He continued to think: It's a pity that Fan Lei also ignored a key link - the problem of information asymmetry. He didn't even know until this moment that he was the so-called "betrayer" in Lan Silin's eyes.

The ease with which this second puzzle was solved was also due to Li Weiyin's idea of thinking backwards and exploiting loopholes.

But skipping the whole process of exploration will inevitably have a little side effect, and he still doesn't know why Fan Lei is a "betrayer".

Even, in the entire arson and school skipping incident, Li Weiyin speculated that the least suspect was Fan Lei. The incident he was the first to find Fan Lei to inquire about was just with the mentality that there would be no problem if he tried it, but he didn't think that he would directly hit the dead mouse with a blind cat and hit it crookedly.

So, Li Weiyin tried to extract some useful information from Fan Lei's mouth.

"Did he tell you anything that night?"

"What else can I say, I smiled at me all night, and I panicked at the thought of his schizophrenic appearance." Fan Lei sighed, and suddenly remembered:

"Oh...... Yes. He also asked me a few things about Stone Town. ”

"Stone Town......" Li Weiyin frowned.

"Here we are."

During the conversation, the two had already arrived at the sand pool.

Fan Lei hurried back to eat, and didn't want to have too much to do with Lan Silin's related matters, so he stopped chatting, walked straight to the southeast corner of the sand pool, closed his eyes, and recalled carefully for a while, muttering in his mouth:

"Third from left, fourth from the front."

He took three steps to the left, four steps forward, stepped on the sand below, and pointed with his hand:

"That's it."

Li Weiyin asked:

"He calculates his position based on your stride?"

"Yes." Fan Lei sighed: "The credit plastic seal paper was wrapped and folded in half, and I watched him bury it." At the bottom of the sand pit, you're going to have to work a little hard. ”

Li Weiyin nodded, Fan Lei was silent for a few seconds, and then said:

"Li Weiyin. It doesn't matter if you don't listen to what I say. The one named Lan Silin is not a simple character. If he really wants to count people, he will count them to death. I don't know what he wants you to do, but you have to be careful. ”

Li Weiyin didn't take this sentence to heart, he had already determined that Lan Silin was not a fairy monster, and human calculations had limits after all. Seeing that Li Weiyin didn't react, Fan Lei sighed, ignored him anymore, and rushed to the canteen.

Occasionally, there was the noise of students in the distance on the playground, and he turned his eyes to the sand pit, and the image of the man holding a wooden stick writing and drawing on the sand pit came to his mind.

When he wrote those ciphers on the sand, what step did he calculate?

Soon it will be known. He's getting closer and closer to the truth.

Thinking of this, Li Weiyin's chest appeared with that warm feeling again. He suppressed the frenzy in his heart, crouched down as calmly as he could, and used his hands to scoop up the sand in front of him.

More than ten minutes later, the sand pool bottomed out, and Li Weiyin's fingertips embedded in the sand touched an object, and he carefully picked it up, his heart beating faster and faster.

He put the object in his pocket, walked briskly out of the playground with a calm face, walked into the nearby toilet, entered the cubicle, locked the door, sat down on the toilet lid, and took out the letter.

He exhaled softly and removed the plastic bag from it.

This time the letter was more formal—at least in an envelope.

He took out the envelope and read the first line of the words in the dim light of the toilet, and his face turned blue for a moment.

"By the time you read this line, the cheater has already lost the round......"