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IMO 1977 — Shortlisted problems Question 11

IMO Shortlist · IMO 1977 — Shortlisted problems

Question 11

(NET 3) Let $n$ be an integer greater than $1$. Define
$$x_1=n,\quad y_1=1,\quad x_{i+1}=\left[\frac{x_i+y_i}{2}\right],\quad y_{i+1}=\left[\frac n{x_{i+1}}\right]\qquad i=1,2,\ldots,$$
where $[z]$ denotes the largest integer less than or equal to $z$. Prove that
$$\min\{x_1,x_2,\ldots,x_n\}=[\sqrt n].$$