#include <algorithm>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

typedef long long ll;

#define sz size()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(c) (c).begin(), (c).end()
#define rep(i,a,b) for(ll i=(a);i<(b);++i)
#define per(i,a,b) for(ll i=(b-1);i>=(a);--i)
#define clr(a, b) memset((a), (b) ,sizeof(a))
#define ctos(c) string(1,c)
#define print(x) cout<<#x<<" = "<<x<<endl;

#define MOD 1000000007

string ntos(long long n){
  string s;
  stringstream ss;
  ss << n;
  ss >> s;
  return s;
}

long long ston(string s){
  long long n;
  sscanf(s.c_str(), "%lld", &n);
  return n;
}

int main() {
  ll n;
  cin>>n;
  ll a = n/1000000000LL;
  if(a==0){
    cout<<0<<endl;
    return 0;
  }
  string s = ntos(a);
  string ss;
  rep(i,0,s.sz/2+s.sz%2){
    ss += s[i];
  }
  per(i,0,s.sz/2){
    ss += s[i];
  }
  ll b = ston(ss);
  ll c = b*1000000000+b;
  int flag = 0;
  if(n>=c){
    flag = 1;
  }
  vector<ll> v;
  rep(i,1,10){
    v.pb(i);
  }
  rep(i,1,100000){
    string s1 = ntos(i);
    string s2 = ntos(i);
    reverse(all(s2));
    string s3 = s1+s2;
    v.pb(ston(s3));
    rep(j,0,10){
      string s4 = ntos(j);
      v.pb(ston(s1+s4+s2));
    }
  }
  ll ans = 0;
  rep(i,0,v.sz){
    if(v[i]<=b)ans++;
  }
  if(flag==0)ans--;
  cout << ans << endl;
  return 0;
}