#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 = true;
#define dump(a) if (DEBUG) cout << (a) << endl;

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

ll N;

void solve() {
  ll p = (ll)1e9 + 1;
  ll count = 0;
  cin >> N;

  rep2(n, 1, 10) {
    if (N >= n * p) {
      dump(n);
      count++;
    }
  }
  rep2(i, 1, (int)1e4) {
    string s1, s2;
    s1 = s2 = to_string(i);
    reverse(all(s2));
    ll n = stoll(s1 + s2);
    if (N >= n * p) {
      dump(n);
      count++;
    }
    rep(i, 10) {
      ll n = stoll(s1 + to_string(i) + s2);
      if (N >= n * p) {
        dump(n);
        count++;
      }
    }
  }

  cout << count << endl;
}

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