2x+2$2x + 2$

bobo has $n$ integers $1, 2, \dots, n$ and uses them to play a game.

He would like to choose a subset $S$ of $\\{1, 2, \dots, n\\}$ such that for all $x \in S$, $(2x + 2) \notin S$.

Now he is curious about the maximum size of $S$.

The first line contains an integer $n$ ($1 \leq n < 10^{100})$.

A single integer denotes the maximum size.