18. Among 65 residents of the village, two are tricksters, and the rest are knights. A knight always tells the truth, while a trickster can either tell the truth or lie. You can show any resident a list of a group of residents (including a group of one person) and ask if they are all knights. How can you find both tricksters by asking no more than 30 questions?
18. In fact, 16 questions are enough (and this is not the minimum).

In the first four questions, we will find a knight. We will do this as follows: ask the first and second residents about the third. If both answered that he is a knight, then he is a knight (otherwise, all three are liars, which is impossible).

If not, then ask the fourth and fifth residents about the sixth. If someone here said that he is a liar, then among $1,2,3$ there is a liar and among $4,5,6$ there is a liar, so the remaining 59 residents are knights, and the remaining questions will definitely be enough. Otherwise, the sixth is a knight.

The remaining questions will be asked to the found knight about the other 64 residents. Using dichotomy, we will find one liar in 6 questions, and in the next 6 questions - another one.