#include <iostream>
#include <cmath>
using namespace std;

int count_numbers(int x) {
    int count = 0;
    for (int i = 0; i < x; i++) {
        int n = i; int ten=0;
        bool decreasing = false;
        bool increasing = true;
        int prev_digit = n % 10;
        n /= 10;
        while (n > 0) {
            int digit = n % 10;
			if (prev_digit > digit) {
				decreasing = true;
				increasing = false;
			}
			if (decreasing && prev_digit < digit) {
                decreasing = false;
                break;
            }
            prev_digit = digit;
            n /= 10;
            ten++;
        }
        if (decreasing||increasing) {
            count++;
        }
    }
    return count;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int x; cin >> x;
    cout << count_numbers(x);
    return 0;
}