#P461. 练83.3 特殊的集合

练83.3 特殊的集合

Description

Given a set AA = {11, 22, ..., nn}, let BB be a subset of AA. For any element xx in BB, 2x2x must not be in BB.
Find the maximum number of elements that can be in set BB.

Input Format

A single integer nn (1n1091 ≤ n ≤ 10^9).

Output Format

A single integer representing the maximum number of elements in set BB.

Sample

100
67