use std::collections::HashSet;

fn main() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s: &str = s.trim();

    let alphabets: HashSet<char> = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".chars().collect();
    let result: HashSet<char> = s.chars().filter(|c| alphabets.contains(c)).collect();

    if s.len() > result.len() {
        println!("NO");
    } else {
        println!("YES");
    }
}