#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int f(long long n){
  string s = to_string(n);
  int l = 0;
  int r = s.length() - 1;
  while(l < r){
    if(s[l] != s[r]) return 0;
    l++;
    r--;
  }
  return 1;
}

int main(void){
  long long n;
  cin >> n;
  int ans = 0;
  long long b = 1e+9 + 1;
  int c = n / b;
  for(int i = 1; i <= c; i++) ans += f(b * i);
  cout << ans << endl;
  return 0;  
}