any pair of (1,2),(2,4),...,(1000,2000) contains 1 from set {1,2,...,2000}
Source: 2015 Belarus TST 2.1
November 5, 2020
combinatorics
Problem Statement
N numbers are marked in the set so that any pair of the numbers contains at least one marked number. Find the least possible value of .I.Gorodnin