#include <iostream>

using namespace std;

int main()
{
	int n;
	int cnt = 0;
	cin >> n;
	for (int i = 1; i <= n; i++){
		string s = to_string(i);
		if (s.size() % 2) cnt++;
	}

	cout << cnt << endl;
}


### Prompt

Your task is to create a CPP solution to the following problem:

Given is an integer N. Find the number of positive integers less than or equal to N that have an odd number of digits (in base ten without leading zeros).

Constraints

* 1 \leq N \leq 10^5

Input

Input is given from Standard Input in the following format:


N


Output

Print the number of positive integers less than or equal to N that have an odd number of digits.

Examples

Input

11


Output

9


Input

136


Output

46


Input

100000


Output

90909

### Response

```cpp
#include <iostream>

using namespace std;

int main()
{
	int n;
	int cnt = 0;
	cin >> n;
	for (int i = 1; i <= n; i++){
		string s = to_string(i);
		if (s.size() % 2) cnt++;
	}

	cout << cnt << endl;
}


```