One day after school, A.B.C.D decided to try the four corners game. They came to a small room next to the school together, turned off the lights and parted.

There is a prisoner acting in the four corners game. The prisoner in this story should be B.

The first round:

A goes to B, hands the stick to B, B goes to C, hands it to C, hands it to D, hands it to D, D goes to the corner where Station A is located, coughs, and then walks in the direction of A. ..

The second round:

A goes to B for the second time and passes it to B.

B goes to C and passes it to C (then B quietly walks back to its original position, that is, there is no one in this corner)

C, find d and pass it to d.

D find a and pass it to a.

Third round

A went to B for the third time and passed it to B. (Originally, this position should be empty, but since B passed it to C and came back, A passed it directly to B without coughing. )

B went to the place where C was in the second round, which is where B should have been. Because B has gone back, there is no one in this corner at this time. B didn't cough, so pass it on to C.

C, find d and pass it to d.

D find a and pass it to a.

As long as B keeps repeating two or three rounds, no one will cough and pass it on.

As for why there was a loud noise and B fell to the ground, I initially thought that B was found. For example, after A passed to B, I followed B's actions and found that B walked through an empty corner without coughing, then hit him with C (muffled voice), and then threw what hit him out of the window (the window was broken). But I found it wrong, because B handed it to D, unless C also found out that B was playing tricks and left the position early to play B with A. I thought about it, and the reasonable explanation was that B took the slash and gave the stick directly to D, and then A and C found out and played in the middle of the room. . . =v=

Suppose supernatural factors are introduced, that is, if there is really one more person, I still can't analyze it, mainly because B gave something to D at the end, which limited many assumptions. Let me think again ~