MathDB
n numbered students , n pieces of paper

Source: (2021-) 2022 XV 15th Dürer Math Competition Finals Day 1 E3

November 29, 2022
combinatorics

Problem Statement

nn students, numbered from 11 to nn are sitting next to each other in a class. In the beginning the 11st student has nn pieces of paper in one pile. The goal of the students is to distribute the nn pieces in a way that everyone gets exactly one. The teacher claps once in a minute and for each clap the students can choose one of the following moves (or do nothing): \bullet They divide one of their piles of paper into two smaller piles. \bullet They give one of their piles of paper to the student with the next number. At least how many times does the teacher need to clap in order to make it possible for the students to distribute all the pieces of paper amongst themselves?