use proconio::{fastout, input, marker::Bytes};

#[fastout]
fn main() {
    input! {
        c: Bytes,
    }

    println!("{}", output(solve(c)))
}

fn solve(c: Vec<u8>) -> u8 {
    (c.into_iter().filter(|&c| c != b'0').count() - 1) as u8
}

fn output(ans: u8) -> u8 {
    ans
}