use proconio::{fastout, input};

#[fastout]
fn main() {
    input! {
        a: [char; 4],
    }

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

fn solve(a: Vec<char>) -> bool {
    a[0] < a[1] && a[2] > a[3]
}

fn output(ans: bool) -> &'static str {
    match ans {
        true => "YES",
        false => "NO",
    }
}