#include <bits/stdc++.h>
using namespace std;

int main(){
    int n;
    cin >> n;
    cout << min(9, n) + max(min(900, n-99), 0) + max(min(90000, n-9999), 0);
    return 0;
}
### Prompt

Develop a solution in Cpp to the problem described below:

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 <bits/stdc++.h>
using namespace std;

int main(){
    int n;
    cin >> n;
    cout << min(9, n) + max(min(900, n-99), 0) + max(min(90000, n-9999), 0);
    return 0;
}
```