Operations on the real line
Source: Brazil National Olympiad 2019 #2
November 14, 2019
combinatorics
Problem Statement
Given are the real line and the two unique marked points and . We can perform as many times as we want the following operation: we take two already marked points and and mark the reflection of over . Let be the minimum number of operations needed to mark on the real line the number (which is the number at a distance from and it is on the right of if and on the left of if ). For example, and . Find .