use proconio::{fastout, input};

#[fastout]
fn main() {
    input! {
        n: u32,
    }

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

fn solve(n: u32) -> u32 {
    let mut dp = [u32::default(); 4];
    dp[0] = n;
    for i in 1..dp.len() {
        dp[i] = dp[i - 1]
            .to_string()
            .bytes()
            .map(|x| (x - b'0') as u32)
            .sum();
    }
    *dp.last().unwrap()
}

fn output(ans: u32) -> u32 {
    ans
}