7.5. A hundred people are standing in a circle, each of whom is either a knight or a liar (liars always lie, and knights always tell the truth). Each of those standing said: “I have a liar as a neighbor.” Find the minimum possible number of liars among these 100 people.
Answer: 34.

Solution: Note that 3 knights cannot stand next to each other, as in this case, the middle knight would be lying. Therefore, among any 3 standing next to each other, there is a liar. Take any liar, and divide the remaining 99 people into 33 groups of three standing next to each other. Since there is at least one liar in each group of three, the total number of liars in the circle is no less than $1+33=34$.

Exactly 34 liars can stand, for example, as follows: -L(KLK)(KLK)... (KLK)-.

Comment: It is only proven that the number of liars is no less than $34-4$ points.

Only an example of an arrangement with 34 liars is given -2 points.