fn run() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let mut a: Vec<usize> = s.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    a.sort();
    for a in a.windows(2) {
        if a[0] + 1 != a[1] {
            println!("No");
            return;
        }
    }
    println!("Yes");
}

fn main() {
    run();
}