#include <bits/stdc++.h>

using namespace std;

int res;
const int N = 110;
int a[N];

//判断是不是数位递增数
bool judge(int x) {
    string s = to_string(x);
    for (int i = 0; i < s.size() - 1; i++)
        if (s[i] > s[i + 1]) return false;
    return true;
}

int main() {
    int n;
    cin >> n;
    for (int i = 10; i <= n; i++)
        if (judge(i)) res++;
    printf("%d", res);
    return 0;
}