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 <iostream>
using namespace std;

int main(){
    int n, ans = 0;
    cin >> n;
    for (int i = 1; i <= n; i++)
        ans += to_string(i).size() % 2;
    cout << ans << endl;
    return 0;
}
