Question 131
Let $n \ge 2$. There are $2n$ people standing in a circle, each holding a different painting in an art conference. Each person has their own fixed preference order of the paintings, which can be different from person to person. A trade of paintings between two adjacent people can happen if and only if both people are getting a painting they prefer more. What is the maximum number of trades that can happen?
(Proposed by Nyamdavaa Amar)
(Proposed by Nyamdavaa Amar)