// szivarvanyszamok.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <queue>
#include <string>

#define ll long long
using namespace std;

ll i, n;
bool ok, ok2 = false;
int main()
{
    cin >> n;
    i = 0;
    ll db = 0;
    
    while (i < n)
    {
        ok = ok2 = false;
        string s = to_string(i);
        for (int j=1;j<s.size();++j)
        {
            if (s[j] >= s[j - 1])
                ok = true;
            else if (s[j] < s[j - 1] && ok)
            {
                ok2 = true;
                break;
            }
        }
        ++i;
        if (!ok2)db++;
    }
    cout << db;
    return 0;
}

// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu

// Tips for Getting Started: 
//   1. Use the Solution Explorer window to add/manage files
//   2. Use the Team Explorer window to connect to source control
//   3. Use the Output window to see build output and other messages
//   4. Use the Error List window to view errors
//   5. Go to Project > Add New Item to create new code files, or Project > Add Existing Item to add existing code files to the project
//   6. In the future, to open this project again, go to File > Open > Project and select the .sln file