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USAMO 2012 — Days 1 and 2 Question 1

USAMO · USAMO 2012 — Days 1 and 2

Question 1

Find all integers $n \ge 3$ such that among any $n$ positive real numbers
$a_1$, $a_2$, …, $a_n$ with

\[ \max(a_1,a_2,\dots,a_n)
\le n \cdot \min(a_1,a_2,\dots,a_n), \]

there exist three that are the side lengths of an acute triangle.