fn run() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let s = s.trim().chars().collect::<Vec<_>>();
    let mut ans = 0;
    for c in s.iter().skip(1) {
        if *c != '0' {
            ans += 1;
        }
    }
    println!("{}", ans);
}

fn main() {
    run();
}