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MathNet 2019-part-01 — 184 problems (EN–VI) Question 19

Math Olympiad Vault · MathNet 2019-part-01 — 184 problems (EN–VI)

Question 19

The natural numbers from $1$ to $300$ inclusive are placed around a circle. We say that such an arrangement is *alternating* if each number is smaller than both of its neighbours or larger than both of its neighbours. We call a pair of neighbouring numbers a *good pair* if, after removing that pair from the circle, the remaining numbers form an alternating arrangement.

Determine the smallest possible number of good pairs in an alternating arrangement of the numbers from $1$ to $300$ inclusive.