#include<bits/stdc++.h>
using namespace std;
bool hui(int m){
	if(m<10) return true;
	int s = m;
	int ss = 0;
	while(m){
		ss+=m%10;
		ss*=10;
		m/=10;
	}
	if(s == ss) return true;
	return false;
}
int main(){
	int n,sum = 0;
	cin>>n;
	for(int i = 1;i<=n;i++){
		if(hui(i)) sum++;
	}
	cout<<sum;
	return 0;
}