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MathNet 2015-part-03 — 191 problems (EN–VI) Question 24

Math Olympiad Vault · MathNet 2015-part-03 — 191 problems (EN–VI)

Question 24

Let $a_{1}, a_{2}, \ldots, a_{n}$ be strictly positive integers. For every $k=1,2, \ldots, n$, let
$$
m_{k}=\max _{1 \leq \ell \leq k} \frac{a_{k-\ell+1}+a_{k-\ell+2}+\cdots+a_{k}}{\ell} .
$$
Show that for every $\alpha\gt 0$, the number of integers $k$ such that $m_{k}\gt \alpha$ is strictly less than $\frac{a_{1}+a_{2}+\cdots+a_{n}}{\alpha}$.