#include<iostream>
using namespace std;

int main()
{
  int n;
  cin>> n;
  if(n < 100)cout << min(9,n) << endl;
  else if(n < 10000) cout<< min(909,n-90) << endl;
  else cout << min(90909,n-9090) << endl;
}
### Prompt

Create a solution in Cpp for 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;
  cin>> n;
  if(n < 100)cout << min(9,n) << endl;
  else if(n < 10000) cout<< min(909,n-90) << endl;
  else cout << min(90909,n-9090) << endl;
}
```