#include<bits/stdc++.h>

using namespace std;

int main(){
  unsigned long long N, add = 1000000001, ans = 0;
  cin >> N;
  for(unsigned long long i = add; i <= N; i += add){
     stringstream ss;
     ss << i;
     string info = ss.str();
     string rinfo = info;
     reverse(rinfo.begin(), rinfo.end());
     if(info == rinfo) ans++;
  }
  cout << ans << "\n";
}