#include<bits/stdc++.h>
#define LL long long
using namespace std;
int Ans,n;
int main() {
	scanf("%d",&n);
	for(int i=1; i<=n; ++i) {
		int w=0,t=i;
		while(t)t/=10,++w;
		if(w&1)++Ans;
	}
	printf("%d",Ans);
}
### Prompt

Develop a solution in CPP to the problem described below:

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

### Response

```cpp
#include<bits/stdc++.h>
#define LL long long
using namespace std;
int Ans,n;
int main() {
	scanf("%d",&n);
	for(int i=1; i<=n; ++i) {
		int w=0,t=i;
		while(t)t/=10,++w;
		if(w&1)++Ans;
	}
	printf("%d",Ans);
}
```