#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

vector<ll> v;

void dfs(const string& x){
  if(x.size() >= 8) return;
  rep(i,10){
    string y = (string("") + (char)('0'+i)) + x + (string("") + (char)('0'+i));
    if(y[0] != '0' && y.size()<=9){
      stringstream ss(y);
      ll z;
      ss >> z;
      v.push_back(z);
    }
    dfs(y);
  }
}


int main(){
  ll N;
  cin >> N;

  dfs("");
  rep(i,10){
    if(i>0) v.push_back(i);
    dfs(string("") + (char)('0'+i));
  }
  
  ll base = 1000000001LL;
  ll ret = 0;
  rep(i,v.size()){
    ll x = base * v[i];
    if(x <= N) ret++;
  }

  cout << ret << endl;
  
  return 0;
}