use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: u64 = itr.next().unwrap().parse().unwrap();
    let mut q: std::collections::VecDeque<u64> = (1..10).collect();

    let mut ans = 0;
    while let Some(x) = q.pop_front() {
        if x * 1000000001 > n {
            println!("{}", ans);
            return;
        }
        ans += 1;
        q.push_back(x * 10 + x);
    }
}