#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define MOD 1000000007
#define INF (1LL<<25)     //33554432
#define PI 3.14159265359
#define EPS 1e-12
//#define int ll

//二分累乗法 xのe乗
ll binpow(ll x, ll e)
{
  ll a = 1, p = x;

  while(e > 0) {
    if(e%2 == 0) {p = (p*p) % MOD; e /= 2;}
    else {a = (a*p) % MOD; e--;}
  }

  return a % MOD;
}

signed main(void)
{
  ll n;
  cin >> n;

  ll a = n/1000000001, ans = 0;
  //cout << "a:" << a << endl;
  FOR(i, 10, 19) {
    ll b = binpow(10, (i-10+1));
    //cout << "b:" << b << endl;
    for(int j=0; j<=sqrt(a); ++j) {
      if(j >= b) break;
      string s = to_string(j);
      bool flag = true;
      REP(k, s.size()/2) {
        if(s[k] != s[s.size()-k-1]) flag = false;
      }
      if(flag) {
        string t(18-i, '0');
        string r = s + t + s;
        if(stoll(r)%1000000001 == 0 && r[0] != '0') {
          ans++;
          //cout << s << " " << t << " " << s << endl;
        }
      }
    }
  }

  cout << ans << endl;

  return 0;
}