We have $N$ players, all of whom are friends with eachother. Each friendship can level up once, whenever the two friends are in the same raid together. At most 20 people can be in a raid together, and a player can only be in one raid at a time.
What is the minimum number of raids to make all friendships level up?
Say any number of raids can be going on at once and that each raid takes unit time. What is the minimum amount of time to make all friendships level up?
Edit: This is a duplicate of this question: Algorithm for a group of people meeting each other person in the least amount of iterations