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CSMO 2017 Grade 10 Problem 4

Source: CSMO 2017 Grade 10 Problem 4

August 6, 2017
algebramaximum value

Problem Statement

Let a1,a2,,a2017a_1,a_2,\dots,a_{2017} be reals satisfied a1=a2017a_1=a_{2017}, ai+ai+22ai+11|a_i+a_{i+2}-2a_{i+1}|\le 1 for all i=1,2,,2015i=1,2,\dots,2015. Find the maximum value of max1i<j2017aiaj\max_{1\le i<j\le 2017}|a_i-a_j|.