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IMO 2023 — Complete Shortlist Question 7

IMO Shortlist · IMO 2023 — Complete Shortlist

Question 7

Let $N$ be a positive integer. Prove that there exist three permutations $a_{1}, a_{2}, \ldots, a_{N}$; $b_{1}, b_{2}, \ldots, b_{N}$; and $c_{1}, c_{2}, \ldots, c_{N}$ of $1,2, \ldots, N$ such that

$$
\left|\sqrt{a_{k}}+\sqrt{b_{k}}+\sqrt{c_{k}}-2 \sqrt{N}\right|\lt 2023
$$

for every $k=1,2, \ldots, N$.