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USAMO 1998 — Days 1 and 2 Question 6

USAMO · USAMO 1998 — Days 1 and 2

Question 6

Let $n\ge5$ be an integer. Find the largest integer $k$, as a function of $n$, for which there exists a convex $n$-gon $A_1A_2\cdots A_n$ with exactly $k$ of the quadrilaterals $A_iA_{i+1}A_{i+2}A_{i+3}$ having an inscribed circle. Indices are taken modulo $n$.