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

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