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,a;
	cin>>n;
	int c1=0;
	for(int i=1;i<=n;i++)
	{
	 a=floor(log10(i) + 1);
	 if(a%2!=0)
	 c1++;
	}cout<<c1;
	return 0;
}
