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 a,ss;
	cin>>a;
	for(int i=1;i<=a;i++)
	{
		if(i<10 || i>99 && i<1000 || i>9999 && i<100000)ss++;
	}
	cout<<ss;
	return 0;
}