import java.util.Scanner;
public class Main{

	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		int A=stdIn.nextInt();
		int B=stdIn.nextInt();
		int C=stdIn.nextInt();
		int D=stdIn.nextInt();
		
		while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		}
		if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes");

	}

} import java.util.Scanner; Scanner java.util public class Main{

	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		int A=stdIn.nextInt();
		int B=stdIn.nextInt();
		int C=stdIn.nextInt();
		int D=stdIn.nextInt();
		
		while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		}
		if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes");

	}

} Main public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		int A=stdIn.nextInt();
		int B=stdIn.nextInt();
		int C=stdIn.nextInt();
		int D=stdIn.nextInt();
		
		while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		}
		if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes");

	} main {
		Scanner stdIn=new Scanner(System.in);
		int A=stdIn.nextInt();
		int B=stdIn.nextInt();
		int C=stdIn.nextInt();
		int D=stdIn.nextInt();
		
		while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		}
		if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes");

	} Scanner stdIn=new Scanner(System.in); stdIn new Scanner(System.in) int A=stdIn.nextInt(); A stdIn.nextInt() stdIn.nextInt stdIn int B=stdIn.nextInt(); B stdIn.nextInt() stdIn.nextInt stdIn int C=stdIn.nextInt(); C stdIn.nextInt() stdIn.nextInt stdIn int D=stdIn.nextInt(); D stdIn.nextInt() stdIn.nextInt stdIn while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		} A>0&&C>0 A>0 A 0 C>0 C 0 {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		} C=C-B C C-B C B if(C<=0)break; C<=0 C 0 break; A=A-D A A-D A D if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes"); A<=0 A 0 System.out.println("No") System.out.println System.out System System.out "No" System.out.println("Yes") System.out.println System.out System System.out "Yes" String[] args args public class Main{

	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		int A=stdIn.nextInt();
		int B=stdIn.nextInt();
		int C=stdIn.nextInt();
		int D=stdIn.nextInt();
		
		while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		}
		if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes");

	}

} public class Main{

	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		int A=stdIn.nextInt();
		int B=stdIn.nextInt();
		int C=stdIn.nextInt();
		int D=stdIn.nextInt();
		
		while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		}
		if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes");

	}

} Main
import java.util.Scanner;
public class Main{

	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		int A=stdIn.nextInt();
		int B=stdIn.nextInt();
		int C=stdIn.nextInt();
		int D=stdIn.nextInt();
		
		while(A>0&&C>0) {
			C=C-B;
			if(C<=0)break;
			A=A-D;
		}
		if(A<=0)
			System.out.println("No");
		else
			System.out.println("Yes");

	}

}