import java.util.Scanner;
public class Main {
	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);

		int tHP = sc.nextInt();
		int tAt = sc.nextInt();
		int aHP = sc.nextInt();
		int aAt = sc.nextInt();


		while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		}

	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);

		int tHP = sc.nextInt();
		int tAt = sc.nextInt();
		int aHP = sc.nextInt();
		int aAt = sc.nextInt();


		while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		}

	}
} Main public static void main(String[] args){

		Scanner sc = new Scanner(System.in);

		int tHP = sc.nextInt();
		int tAt = sc.nextInt();
		int aHP = sc.nextInt();
		int aAt = sc.nextInt();


		while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		}

	} main {

		Scanner sc = new Scanner(System.in);

		int tHP = sc.nextInt();
		int tAt = sc.nextInt();
		int aHP = sc.nextInt();
		int aAt = sc.nextInt();


		while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		}

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int tHP = sc.nextInt(); tHP sc.nextInt() sc.nextInt sc int tAt = sc.nextInt(); tAt sc.nextInt() sc.nextInt sc int aHP = sc.nextInt(); aHP sc.nextInt() sc.nextInt sc int aAt = sc.nextInt(); aAt sc.nextInt() sc.nextInt sc while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		} true {
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		} aHP -= tAt aHP tAt tHP -= aAt tHP aAt if(aHP <= 0){
				System.out.print("Yes");
				return;
			} aHP <= 0 aHP 0 {
				System.out.print("Yes");
				return;
			} System.out.print("Yes") System.out.print System.out System System.out "Yes" return; if(tHP <= 0){
				System.out.print("No");
				return;
			} tHP <= 0 tHP 0 {
				System.out.print("No");
				return;
			} System.out.print("No") System.out.print System.out System System.out "No" return; String[] args args public class Main {
	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);

		int tHP = sc.nextInt();
		int tAt = sc.nextInt();
		int aHP = sc.nextInt();
		int aAt = sc.nextInt();


		while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		}

	}
} public class Main {
	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);

		int tHP = sc.nextInt();
		int tAt = sc.nextInt();
		int aHP = sc.nextInt();
		int aAt = sc.nextInt();


		while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		}

	}
} Main
import java.util.Scanner;
public class Main {
	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);

		int tHP = sc.nextInt();
		int tAt = sc.nextInt();
		int aHP = sc.nextInt();
		int aAt = sc.nextInt();


		while(true){
			aHP -= tAt;
			tHP -= aAt;
			if(aHP <= 0){
				System.out.print("Yes");
				return;
			}
			if(tHP <= 0){
				System.out.print("No");
				return;
			}
		}

	}
}
