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OlympiadBench / 2198 / The n contestants of an EGMO are named C₁,…,C_(n). After the…

Problem

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question

The nn contestants of an EGMO are named C1,,CnC_{1}, \ldots, C_{n}. After the competition they queue in front of the restaurant according to the following rules. - The Jury chooses the initial order of the contestants in the queue. - Every minute, the Jury chooses an integer ii with 1in1 \leq i \leq n. - If contestant CiC_{i} has at least ii other contestants in front of her, she pays one euro to the Jury and moves forward in the queue by exactly ii positions. - If contestant CiC_{i} has fewer than ii other contestants in front of her, the restaurant opens and the process ends. Determine for every nn the maximum number of euros that the Jury can collect by cunningly choosing the initial order and the sequence of moves.
Plain-text mathematical notation (without MathML)
The n contestants of an EGMO are named C₁,…,C_(n). After the competition they queue in front of the restaurant according to the following rules.

- The Jury chooses the initial order of the contestants in the queue.
- Every minute, the Jury chooses an integer i with 1≤i≤n.
    - If contestant C_(i) has at least i other contestants in front of her, she pays one euro to the Jury and moves forward in the queue by exactly i positions.
    - If contestant C_(i) has fewer than i other contestants in front of her, the restaurant opens and the process ends.
Determine for every n the maximum number of euros that the Jury can collect by cunningly choosing the initial order and the sequence of moves.
Original LaTeX notation
The $n$ contestants of an EGMO are named $C_{1}, \ldots, C_{n}$. After the competition they queue in front of the restaurant according to the following rules.

- The Jury chooses the initial order of the contestants in the queue.
- Every minute, the Jury chooses an integer $i$ with $1 \leq i \leq n$.
    - If contestant $C_{i}$ has at least $i$ other contestants in front of her, she pays one euro to the Jury and moves forward in the queue by exactly $i$ positions.
    - If contestant $C_{i}$ has fewer than $i$ other contestants in front of her, the restaurant opens and the process ends.
Determine for every $n$ the maximum number of euros that the Jury can collect by cunningly choosing the initial order and the sequence of moves.

answer type

Expression

is multiple answer

false

language

English

question type

Open-ended

subject

Math

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