#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "math.h"
#include "utility"
#include "string"
#include "map"
#include "unordered_map"
#include "iomanip"
#include "random"

using namespace std;
const long long int MOD = 1000000007;

long long int N;
string a;
string b;
int ans;
int box;

int main() {
	cin >> N;
	N /= 1000000001;
	for (int i = 1; i <= N; i++) {
		box = i;
		while (box) {
			a.push_back(char(box % 10));
			b.insert(begin(b), char(box % 10));
			box /= 10;
		}
		if (a == b)ans++;
		a.clear();
		b.clear();
	}
	cout << ans << endl;
	return 0;
}