MathDB
Polish MO Finals 2014, Problem 2

Source: Polish MO Finals 2014

July 27, 2016
contestsalgebra

Problem Statement

Let k2k\ge 2, n1n\ge 1, a1,a2,,aka_1, a_2,\dots, a_k and b1,b2,,bnb_1, b_2, \dots, b_n be integers such that 1<a1<a2<<ak<b1<b2<<bn1<a_1<a_2<\dots <a_k<b_1<b_2<\dots <b_n. Prove that if a1+a2++ak>b1+b2++bna_1+a_2+\dots +a_k>b_1+b_2+\dots + b_n, then a1a2ak>b1b2bna_1\cdot a_2\cdot \ldots \cdot a_k>b_1\cdot b_2 \cdot \ldots \cdot b_n.