9475: ABC215 —— B - log2(N)
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Description
Given a positive integer $N$, find the maximum integer $k$ such that $2^k \le N$.
Input
Input is given from Standard Input in the following format:
```
$N$
```
```
$N$
```
Output
Print the answer as an integer.
Constraints
$N$ is an integer satisfying $1 \le N \le 10^{18}$.
Sample 1 Input
6
Sample 1 Output
2
- k=2 satisfies $2^2=4≤6$.
- For every integer k such that $k≥3,\ 2^k>6$ holds.
Sample 2 Input
1
Sample 2 Output
0
Note that $2^0=1$.
Sample 3 Input
1000000000000000000
Sample 3 Output
59