#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n)-1;i>=0;i--)
#define rrep2(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define all(a) (a).begin(),(a).end()
const bool DEBUG = false;
#define dump(a) if (DEBUG) cout << (a) << endl;

typedef long long ll;
typedef pair<int, int> P;

ll N;

bool is_palindrome(ll n) {
  string s1, s2;
  s1 = s2 = to_string(n);
  reverse(all(s2));
  return s1 == s2;
}

ll make_palindrome(int i) {
  string s1, s2;
  s1 = s2 = to_string(i);
  reverse(all(s2));
  return stoll(s1 + s2);
}

void solve() {
  ll p = (ll)1e9 + 1;
  ll count = 0;
  cin >> N;
  ll max_n = ((N / p) * p) % (ll)1e9;
  dump(max_n);

  rep2(n, 1, 10) {
    if (max_n > n) {
      dump(n);
      count++;
    }
  }
  rep2(i, 1, (ll)1e5) {
    ll n = make_palindrome(i);
    if (max_n > n) {
      dump(n);
      count++;
    }
  }

  cout << count << endl;
}

int main() {
  solve();
  return 0;
}