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

int main() {
  int64_t N; { cin >> N; }

  const int X = 1e9 + 1;

  auto rev = [](string s) {
    reverse(s.begin(), s.end());
    return s;
  };

  int res = 0; {
    for (int i = 1; i < 10; ++i) res += (int64_t) i * X <= N;
    for (int i = 1; i < 10000; ++i) {
      int64_t v = stoi(to_string(i) + rev(to_string(i)));
      res += v * X <= N;
      for (int j = 0; j < 10; ++j) {
        v = stoi(to_string(i) + to_string(j) + rev(to_string(i)));
        res += v * X <= N;
      }
    }
  }

  cout << res << endl;
}