#include<bits/stdc++.h>
using namespace std;
int main(){
    int i,n,h=0;
    cin>>n;
    for(i=1;i<=n;i++){
    	if(i<=99){
    		if(i%10==0){
    		    h++;
    		}
    	}else{
    		if(i/10%10==0||i%10==0){
    			h++;
    		}
    	}
    }
    cout<<h;
}
/**************************************************************
	Problem: 1750
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/