Rich knight adds coins
Source: 239 MO 2024 S2
May 22, 2024
combinatorics
Problem Statement
A rich knight has a chest and a lot of coins, so every day he puts into the chest some quantity of coins - among the numbers . If there exist two days on which he added equal quantities of coins (say, coins) and he has added in total at most coins on the days between these two days, he stops putting coins into the chest. Prove that this will necessarily happen eventually.