bobo 有 $n$ 个整数 $1, 2, \dots, n$，并用它们玩一个游戏。 他想选择一个子集 $S \subseteq \{1, 2, \dots, n\}$，使得对于所有的 $x \in S$，都有 $(2x + 2) \notin S$。 他现在对 $S$ 的最大大小很感兴趣。
第一行包含一个整数 $n$ ($1 \le n < 10^{100}$)。
输出一个整数，表示最大大小。
4
3
1000000000
666666667
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