use std::cmp::*;
use std::io::*;

fn main() {
    let mut s: String = String::new();
    stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let s: Vec<char> = itr.next().unwrap().chars().collect();
    let mut ans = 0;
    for i in 1..s.len() {
        ans += if s[i] != '0' { 1 } else { 0 }
    }
    println!("{}", ans);
}