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;
typedef long long int ll;

int main()
{
    int n;
    cin>>n;
    cout<<min(9,n)+max(0,min(900,n-99))+max(0,min(90000,n-9999))<<endl;



return 0;
}
