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MathNet 2004 — Part 01 Question 105

Math Olympiad Vault · MathNet 2004 — Part 01

Question 105

There are $2 n$ different numbers in a row. By one move we can interchange any two numbers or interchange any three numbers cyclically (choose $a, b, c$ and place $a$ instead of $b$, $b$ instead of $c$ and $c$ instead of $a$). What is the minimal number of moves that is always sufficient to arrange the numbers in increasing order?