#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define loop(i,a,b) for(i=a;i<b;i++)
#define rloop(i,a,b) for(i=a;i>=b;i--)
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
const int inf=1000000001;
const ll INF=1e16;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846

int main(){
	ll n;
	int i,j;
	cin>>n;
	ll k=n/inf;
	ll ans=0;
	string s;
	ll a;
	loop(i,0,k){
		a=i*inf;
		s=to_string(a);
		bool flag=true;
		loop(j,0,s.size()){
			if(s[j]!=s[s.size()-1-j]){
				flag=false;
			}
		}
		if(flag){
			ans++;
		}
	}
	cout<<ans<<endl;
}