package test; import java.util.Scanner; public class atc { public static void main(String[] args) { Scanner sc=new Scanner(System.in); long h=sc.nextInt(); long w=sc.nextInt(); long n=sc.nextInt(); long k=sc.nextInt(); long ans=(h+w-1)%n; if(ans==0)ans=n; if(ans==k) System.out.println("YES"); else System.out.println("NO"); } }