import java.util.Scanner;

public class Test {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		long m = sc.nextLong()*sc.nextLong(), n = sc.nextLong(), k = sc.nextLong();
		if(m%n == k%n){
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
}