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ISL 2022 A4

    Let n⩾3n \geqslant 3 be an integer, and let x1,x2,…,xnx_{1}, x_{2}, \ldots, x_{n} be real numbers in the interval [0,1][0,1]. Let s=x1+x2+…+xns=x_{1}+x_{2}+\ldots+x_{n}, and assume that s⩾3s \geqslant 3. Prove that there exist integers ii and jj with 1⩽i<j⩽n1 \leqslant i<j \leqslant n such that 2j−ixixj>2s−32^{j-i} x_{i} x_{j}>2^{s-3} (Trinidad and Tobago)

    Dataset text NuminaMath olympiads. Quoted with source.

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