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,res=0;
  	cin >> n;
  	for(int i=1;i<=n;i++){
    	string a=to_string(i);
      	if(a.size() % 2 !=0) res++;
    }
  	cout << res << endl;
}