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,ans;cin>>N;
  if(N<=99)ans=min(9,N);
  else if(N<=9999)ans=min(909,N-90);
  else ans=min(90909,N-9090);
  cout<<ans<<endl;
}
