use std::io;
use std::str::FromStr;

fn main() {
    let stdin = io::stdin();
    let mut buf = String::new();
    stdin.read_line(&mut buf).ok();

    let mut it = buf.split_whitespace().map(|n| String::from_str(n).unwrap());
    let a = it.next().unwrap();

    let mut ans = 0;
    for i in 0..a.len() {
        let is_num = a.chars().nth(i).unwrap();
        if is_num <= '9' {
            ans += is_num.to_digit(10).unwrap();
        }
    }

    println!("{}", ans);

}