import java.util.Scanner;
public class Main {

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

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

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

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

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

} public class Main {

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

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

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

}
