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