fn main() {
    let mut lrmk = String::new();
    std::io::stdin().read_line(&mut lrmk).ok();
    let lrmk: Vec<usize> = lrmk.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let l = lrmk[0];
    let r = lrmk[1];
    let m = lrmk[2];
    let k = lrmk[3];
    let left = l * k;
    let right = r * k;
    let mut result = false;
    result |= (right - left) / m > 0;
    result |= right % m < left % m;
    result |= left % m == 0;
    if result {
        println!("Yes");
    } else {
        println!("No");
    }
}