#include <iostream>
#include <bits/stdc++.h>
using namespace std;
int jisu(int a)
{
	int s = 1;
	do{
		if(a / 10 > 0){
			s++;
		}
		a /= 10;
	}while(a != 0);
    return (s);
}
int pd(int b)
{
	int flag = 1;
	int m = jisu(b);
	int sum = 3 * b + 3;
	if(jisu(sum) != m){
		flag = 0;
	}
	return (flag);
}
int main()
{
	int n;
	int sum = 0;
	cin >> n;
	for(int i = 1 ;i <= n ;i++){
		int flag = pd(i);
		if(flag == 1){
			sum++;
		}
	}
	cout << sum;
	return 0;
}