What is the largest number of distinct positive integers you can have such that most of their pairwise differences are prime?
For example, among (2, 4, 6, 11, 13, 15) there are 15 pairwise differences, of which 10 are prime.
Mr. Blue has 12 brown gloves and 8 black gloves in a drawer in his closet. If he blindly pulls gloves from the drawer, what's the minimum number of gloves Mr. Blue will have to pick, to be certain he has a pair of gloves of the same color?