Question 11
A mathematics conference has exactly $n$ married couples, where $n\ge8$. All men sit around one circular table with $n$ seats, and all women around another such table. A healthy person becomes infected immediately if at least two of their left neighbor, right neighbor and spouse are infected; otherwise that person remains healthy. Initially $s$ of the $2n$ participants are infected, and eventually everybody becomes infected. What is the minimum possible value of $s$?