import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		int A = input.nextInt();
		int B = input.nextInt();
		int C = input.nextInt();
		int D = input.nextInt();
		
		takahasi(A,B,C,D);
		
	}
	public static void takahasi(int A,int B,int C,int D) {
		C-=B;
		if(C<=0) {
			System.out.println("Yes");
		}
		else {
			aoki(A,B,C,D);
		}
	}
	public static void aoki(int A,int B,int C,int D) {
		A-=D;
		if(A<=0) {
			System.out.println("No");
		}
		else {
			takahasi(A,B,C,D);
		}
	}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz