#include <iostream>
using namespace std;

int main(){
	int i,n,c = 0;
	cin>>n;
	for(i = 1;i <= n;i++){
		if(i <= 99){
			if(i%10==0){
				c++;
			}
		}else{
			if(i/10%10==0||i%10==0){
				c++;
			}
		}
	}
	cout<<c;
}
/**************************************************************
	Problem: 1750
	User: admin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/