2n + 1 students chooses a finite set of consecutive integers
Source: Switzerland - 2013 Swiss MO Final Round p5
December 30, 2022
combinatoricsconsecutivenumber theory
Problem Statement
Each of students chooses a finite, nonempty set of consecutive integers . Two students are friends if they have chosen a common number. Everyone student is friends with at least other students. Show that there is a student who is friends with everyone else.