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();
		int ans = 0;
		for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		}
		if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		}
		stdIn.close();
	}
} 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();
		int ans = 0;
		for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		}
		if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		}
		stdIn.close();
	}
} 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();
		int ans = 0;
		for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		}
		if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		}
		stdIn.close();
	} main {
		Scanner stdIn = new Scanner(System.in);
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		int C = stdIn.nextInt();
		int D = stdIn.nextInt();
		int ans = 0;
		for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		}
		if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		}
		stdIn.close();
	} 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 int ans = 0; ans 0 for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		} ; {
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		} {
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		} C = C - B C C - B C B A = A - D A A - D A D if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			} C <= 0 C 0 {
				ans = 0;
				break;
			} ans = 0 ans 0 break; if(A <= 0){
				ans = 1;
				break;
			} A <= 0 A 0 {
				ans = 1;
				break;
			} ans = 1 ans 1 break; if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		} ans == 0 ans 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" stdIn.close() stdIn.close stdIn 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();
		int ans = 0;
		for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		}
		if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		}
		stdIn.close();
	}
} 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();
		int ans = 0;
		for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		}
		if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		}
		stdIn.close();
	}
} 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();
		int ans = 0;
		for(;;){
			C = C - B;
			A = A - D;
			if(C <= 0){
				ans = 0;
				break;
			}
			else if(A <= 0){
				ans = 1;
				break;
			}
		}
		if(ans == 0){
			System.out.println("Yes");
		}
		else{
			System.out.println("No");		}
		stdIn.close();
	}
}