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 n, ans;


int main() {
	cin >> n;
	for (int i = 1; i <= n; i++)
		ans += (to_string(i).size() & 1);
	cout << ans;
	return 0;
}