MathDB
2023 China TST, Day 1, Problem 2

Source:

March 14, 2023
combinatoricsChina TST

Problem Statement

nn people attend a party. There are no more than nn pairs of friends among them. Two people shake hands if and only if they have at least 11 common friend. Given integer m3m\ge 3 such that nm3n\leq m^3. Prove that there exists a person AA, the number of people that shake hands with AA is no more than m1m-1 times of the number of AA‘S friends.