MathDB
An interstellar hotel

Source: All-Russian Olympiad 2019 grade 10 problem 3

April 23, 2019
combinatoricsconstruction

Problem Statement

An interstellar hotel has 100100 rooms with capacities 101,102,,200101,102,\ldots, 200 people. These rooms are occupied by nn people in total. Now a VIP guest is about to arrive and the owner wants to provide him with a personal room. On that purpose, the owner wants to choose two rooms AA and BB and move all guests from AA to BB without exceeding its capacity. Determine the largest nn for which the owner can be sure that he can achieve his goal no matter what the initial distribution of the guests is.