import java.util.Scanner;
public class Main {
	public static void main(String args[]) {
	Scanner sc=new Scanner(System.in);
	int A=sc.nextInt();
	int B=sc.nextInt();
	int C=sc.nextInt();
	int D=sc.nextInt();
	int i=0;
	int j=0;
	for(;;) {
		i++;
		C-=B;
		if(C<=0) {
			break;
		}
	}
	for(;;) {
		j++;
		A-=D;
		if(A<=0) {
			break;
		}
	}
	if(i<=j) {
		System.out.println("Yes");
	}
	else {
		System.out.println("No");
	}
	}
}
/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