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China Mathematical Olympiad 2016 Q1

Source: China Yingtan ,Dec 16, 2015

December 16, 2015
inequalitiesSequences

Problem Statement

Let a1,a2,,a31;b1,b2,,b31a_1,a_2,\cdots, a_{31} ;b_1,b_2, \cdots, b_{31} be positive integers such that a1<a2<<a312015a_1< a_2<\cdots< a_{31}\leq2015 , b1<b2<<b312015 b_1< b_2<\cdots<b_{31}\leq2015 and a1+a2++a31=b1+b2++b31.a_1+a_2+\cdots+a_{31}=b_1+b_2+\cdots+b_{31}. Find the maximum value of S=a1b1+a2b2++a31b31.S=|a_1-b_1|+|a_2-b_2|+\cdots+|a_{31}-b_{31}|.