fn main() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let mut v = s
        .split_whitespace()
        .map(|x| x.parse::<i32>().unwrap())
        .collect::<Vec<i32>>();
    v.sort();
    let ans = match v.windows(2).all(|v| v[1] - v[0] == 1) {
        true => "Yes",
        _ => "No",
    };
    println!("{}", ans)
}