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 res = 0;
	for (int i = 1; i <= N; i++) {
		res += to_string(i).size() & 1;
	}
	cout << res << endl;
	return 0;
}
