#include <iostream>
using namespace std;
int a[10001];
int ans=0;
int main(){
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		if(i<10&&i%2!=0)
		ans++;
		if(i>=10&&i<100&&(i%10)%2!=0&&(i/10)%2==0)
		ans++;
		if(i>=100&&i<1000&&i%10%2!=0&&i%100/10%2==0&&i/100%2!=0)
		ans++;
		if(i>=1000&&i<10000&&i%10%2!=0&&i%100/10%2==0&&i%1000/100%2!=0&&i/1000%2==0)
		ans++;
		if(i>=10000&&i<100000&&i%10%2!=0&&i%100/10%2==0&&i%1000/100%2!=0&&i%10000/1000%2==0&&i/10000%2!=0)
		ans++;
		if(i>=100000&&i<1000000&&i%10%2!=0&&i%100/10%2==0&&i%1000/100%2!=0&&i%10000/1000%2==0&&i%100000/10000%2!=0&&i/100000%2==0)
		ans++;
		if(i>=1000000&&i<10000000&&i%10%2!=0&&i%100/10%2==0&&i%1000/100%2!=0&&i%10000/1000%2==0&&i%100000/10000%2!=0&&i%1000000/100000%2==0&&i/1000000%2!=0)
		ans++;
		
	}
	cout<<ans;
	return 0;
}