package no384;

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long h = sc.nextLong();
		long w = sc.nextLong();
		long n = sc.nextLong();
		long k = sc.nextLong();
		System.out.println((h + w + n - 1) % n == k % n ? "YES" : "NO");
	}
}