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, c;
int main(){
    cin >> n;
    for (int i=1; i<=n; i++){
        if (to_string(i).length()%2==1){
            c++;
        }
    }
    cout << c;
}