#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>  
#include <cmath>   
#include<cctype>
#include<string>
#include<set>
#include<iomanip>
#include <map>
#include<algorithm>
#include <functional>
#include<vector>
#include<climits>
#include<stack>
#include<queue>
#include <deque>
#include <climits>
#include <typeinfo>
#include <utility> 
#define all(x) (x).begin(),(x).end()
#define rep(i,m,n) for(int i = m;i < n;++i)
#define pb push_back
#define fore(i,a) for(auto &i:a)
#define rrep(i,m,n) for(int i = m;i >= n;--i)
#define INF INT_MAX/2
using namespace std;
using ll = long long;
using R = double;
using Data = pair<ll, vector<int>>;
const ll MOD = 1e9 + 7;
const ll inf = 1LL << 50;
struct edge { ll from; ll to; ll cost; };

vector<ll>s;

ll conv(string p) {
	ll ret = 0;
	reverse(all(p));
	ll dgt = 1;
	fore(x, p) {
		ret += dgt * (x - '0');
		dgt *= 10;
	}
	return ret;
}
ll getdigit(string s) {
	return s.size();
}

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

	ll temp = 1e9 + 1;
	
	rep(i, 1, 10)s.pb(i);
	for(ll i = 1; i < 10000; i++) {
		string s1 = to_string(i);
		string s2 = s1;
		reverse(all(s2));
		s.pb(conv(s1 + s2));
		for (ll j = 0; j <= 9; j++) {
			s.pb(conv(s1 + to_string(j)+s2));
		}
	}
	sort(all(s));

	ll ans = 0;
	fore(x,s) {
		if (x * temp <= n)ans++;
	}
	cout << ans << endl;

	return 0;
}