import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

public class Main {
    static Scanner in = new Scanner(System.in);
    static Set<Integer> list = new HashSet<>();
    static int max;

    public static void main(String[] args) {
        max = (int) (in.nextLong() / ((long) 1e9 + 1));
        for (int i = 1; i < 10; i++) {
            f(1, i);
        }
        int ans = 0;
        List<Integer> sortList = new ArrayList<>(list);
        Collections.sort(sortList);
        for (int i : sortList) {
            if (max >= i) {
                //System.out.println(i);
                ans++;
            }
        }
        System.out.println(ans);
    }

    public static void f(int s, int n) {
        if (s > String.valueOf(max).length()) {
            return;
        }
        if (s == 1) {
            list.add(n);
            f(s + 1, n);
        } else if (s % 2 == 0) {
            String l = String.valueOf(n);
            String r = (new StringBuilder(String.valueOf(n))).reverse().toString();
            list.add(Integer.parseInt(l + r));
            f(s + 1, n);
        } else if (s % 2 == 1) {
            String l = String.valueOf(n);
            String r = (new StringBuilder(String.valueOf(n))).reverse().toString();
            for (int i = 0; i < 10; i++) {
                list.add(Integer.parseInt(l + i + r));
                f(s + 1, n * 10 + i);
            }

        }
    }
}