MathDB
Problem 3

Source: 2023 China Second Round P3

September 10, 2023
combinatoricschang09

Problem Statement

Find the smallest positive integer k{k} with the following properties ::{}{}{}{}{}If each positive integer is arbitrarily colored red or blue,{}{}{}, there may be 9{}{}{}{}9 distinct red positive integers x1,x2,,x9,x_1,x_2,\cdots ,x_9, satisfying x1+x2++x8<x9,x_1+x_2+\cdots +x_8<x_9, or there are 1010{}{}{}{}{}{} distinct blue positive integers y1,y2,,y10y_1,y_2,\cdots ,y_{10} satisfiying y1+y2++y9<y10.{y_1+y_2+\cdots +y_9<y_{10}}.