import java.util.*;
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();
		String ans = "Yes";
		while(A > 0 && C > 0){
			A -= D;
			C -= B;
		}
		if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		}
		System.out.println(ans);
	}
} import java.util.*; util.* java 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();
		String ans = "Yes";
		while(A > 0 && C > 0){
			A -= D;
			C -= B;
		}
		if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		}
		System.out.println(ans);
	}
} 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();
		String ans = "Yes";
		while(A > 0 && C > 0){
			A -= D;
			C -= B;
		}
		if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		}
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		String ans = "Yes";
		while(A > 0 && C > 0){
			A -= D;
			C -= B;
		}
		if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		}
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int A = sc.nextInt(); A sc.nextInt() sc.nextInt sc int B = sc.nextInt(); B sc.nextInt() sc.nextInt sc int C = sc.nextInt(); C sc.nextInt() sc.nextInt sc int D = sc.nextInt(); D sc.nextInt() sc.nextInt sc String ans = "Yes"; ans "Yes" while(A > 0 && C > 0){
			A -= D;
			C -= B;
		} A > 0 && C > 0 A > 0 A 0 C > 0 C 0 {
			A -= D;
			C -= B;
		} A -= D A D C -= B C B if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		} C <= 0 C 0 {
			ans = "Yes";
		} ans = "Yes" ans "Yes" {
			ans = "No";
		} ans = "No" ans "No" System.out.println(ans) System.out.println System.out System System.out ans String args[] args 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();
		String ans = "Yes";
		while(A > 0 && C > 0){
			A -= D;
			C -= B;
		}
		if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		}
		System.out.println(ans);
	}
} 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();
		String ans = "Yes";
		while(A > 0 && C > 0){
			A -= D;
			C -= B;
		}
		if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		}
		System.out.println(ans);
	}
} Main
import java.util.*;
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();
		String ans = "Yes";
		while(A > 0 && C > 0){
			A -= D;
			C -= B;
		}
		if(C <= 0){
			ans = "Yes";
		}else{
			ans = "No";
		}
		System.out.println(ans);
	}
}