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();

		while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		}
		if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
		sc.close();
	}

} import java.util.Scanner; Scanner 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();

		while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		}
		if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
		sc.close();
	}

} 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();

		while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		}
		if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
		sc.close();
	} main {

		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
		int d = sc.nextInt();

		while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		}
		if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
		sc.close();
	} 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 while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		} 0 < c && 0 < a 0 < c 0 c 0 < a 0 a {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		} c -= b c b if(c <= 0) {
				break;
			} c <= 0 c 0 {
				break;
			} break; a -= d a d if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		} 0 < a 0 a {
			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" sc.close() sc.close sc 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();

		while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		}
		if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
		sc.close();
	}

} 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();

		while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		}
		if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
		sc.close();
	}

} Main
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();

		while(0 < c && 0 < a) {
			c -= b;
			if(c <= 0) {
				break;
			}
			a -= d;
		}
		if(0 < a) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
		sc.close();
	}

}