Around a large round table, 60 people are sitting, each of whom is either a knight or a liar. Each of them said: “Of the five people sitting in a row to my right, at least two are liars.” How many knights can sit at this table?
Let's divide 60 people sitting at a table into 10 groups of 6 people each and prove that in each group there are exactly two liars. Let's consider two cases.

1) Suppose the first person in such a group is a knight. Then he told the truth, and among the five people in this group sitting to his right, at least two are liars. At the same time, there cannot be more than two liars in such a group, otherwise the first liar in this group would have told the truth. Therefore, in this group there are exactly two liars.
2) Suppose the first person in such a group is a liar. Then he lied, and among the five people in this group sitting to his right, there is no more than one liar. At the same time, there must be exactly one liar, otherwise the first knight in this group would have lied: behind him sit four knights and no more than one liar. Therefore, in this group, including the first one, there are exactly two liars.

Thus, in each of the ten groups there are exactly 4 knights, making a total of 40 knights.

## Answer

40 knights.