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;
  cin >> N;
  
  int s = 0;
  for (int i = 1; i <= N; ++i) {
    if (to_string(i).length() % 2 == 1) s+=1;
  }
  
  cout << s << endl;
}