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