use std::*;

//https://yukicoder.me/wiki/stdio
fn getline() -> String {
    let mut __ret = String::new();
    std::io::stdin().read_line(&mut __ret).ok();
    return __ret;
}

fn main() {
    let mut s = getline();
    let mut v = 0i64;
    loop {
        match s.pop() {
            Some(n) => {
                let num = n as i64 - 48;
                v += num;
            }
            None => break,
        }
    }
    println!("{}", v);
}