Problem Background

The more determined a magic practitioner is, the luckier they become. ——Hall of Fame Magic Practitioner S

Problem Description

Junior magic practitioner Xiao M's magic number is $2$.

Given a positive integer $n$, Xiao M needs to find the largest even number $m$ such that $2^m < n$.

Please help him with this task.

Input Format

A single line containing a positive integer $n$.

Output Format

A single line containing an even number $m$, representing the answer.

Sample Input and Output

Sample Input #1

7

Sample Output #1

2

Sample Input #2

8

Sample Output #2

2

Sample Input #3

1024

Sample Output #3

8

Notes

[Data Range]

For the first $20\%$ of the data, $n = 2$.

For the first $60\%$ of the data, $n$ is a power of $2$.

For $100\%$ of the data, $2 \le n \le 10^9$.

见题面 Input 部分

见题面 Output 部分