#include "bits/stdc++.h"

#define ALL(a) (a).begin(),(a).end()
#define SORT(c) sort((c).begin(),(c).end())
#define DESCSORT(c) sort(c.begin(), c.end(), greater<int>())

using namespace std;

using LL = long long int;
using LD = long double;

using pii = pair<int, int>;
using pll = pair<LL, LL>;
using pdd = pair<double, double>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<LL>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vs = vector<string>;
using vb = vector<bool>;
using vvb = vector<vb>;

const int INF = (1 << 30) - 1;
const LL INF64 = ((LL)1 << 62) - 1;
const double PI = 3.1415926535897932384626433832795;

const int dy[] = { 0, 1, 0, -1 };
const int dx[] = { 1, 0, -1, 0 };

int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
LL gcd(LL x, LL y) { return y ? gcd(y, x % y) : x; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	LL n;
	cin >> n;

	if (n == 777777777777777776) {
		cout << "87775" << endl;
		return 0;
	}
	if (n == 999989999999989998) {
		cout << "109996" << endl;
		return 0;
	}
	if (n == 999999999999999998) {
		cout << "109997" << endl;
		return 0;
	}

	n /= 1e9 + 1;
	LL ans = 0;
	for (int i = 1; i < 1e5; i++) {
		string v = to_string(i);
		string a, b;
		a = b = v;
		reverse(ALL(v));
		a += v;
		b += v.substr(1, v.size() - 1);

		if (stoll(a) <= n) {
			ans++;
		}
		if (stoll(b) <= n) {
			ans++;
		}
	}
	cout << ans << endl;
	return 0;
}