#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;cin>>N;
  if(N<99)cout<<min(N,9)<<endl;
  else if(N<9999)cout<<min(N-90,909)<<endl;
  else cout<<min(N-9090,90909)<<endl;
}
### Prompt

Please create a solution in CPP 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 <bits/stdc++.h>
using namespace std;
int main(){
  int N;cin>>N;
  if(N<99)cout<<min(N,9)<<endl;
  else if(N<9999)cout<<min(N-90,909)<<endl;
  else cout<<min(N-9090,90909)<<endl;
}
```