import java.util.*;
class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int H1 = sc.nextInt();
		int A1 = sc.nextInt();
		int H2 = sc.nextInt();
		int A2 = sc.nextInt();
		
		while(true)
		{
			H2 -= A1;
			if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			}
			
			H1 -= A2;
			if(H1 <= 0)
			{
				System.out.println("No");
				break;
			}
		}
	}
} import java.util.*; util.* java class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int H1 = sc.nextInt();
		int A1 = sc.nextInt();
		int H2 = sc.nextInt();
		int A2 = sc.nextInt();
		
		while(true)
		{
			H2 -= A1;
			if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			}
			
			H1 -= A2;
			if(H1 <= 0)
			{
				System.out.println("No");
				break;
			}
		}
	}
} Main public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int H1 = sc.nextInt();
		int A1 = sc.nextInt();
		int H2 = sc.nextInt();
		int A2 = sc.nextInt();
		
		while(true)
		{
			H2 -= A1;
			if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			}
			
			H1 -= A2;
			if(H1 <= 0)
			{
				System.out.println("No");
				break;
			}
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int H1 = sc.nextInt();
		int A1 = sc.nextInt();
		int H2 = sc.nextInt();
		int A2 = sc.nextInt();
		
		while(true)
		{
			H2 -= A1;
			if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			}
			
			H1 -= A2;
			if(H1 <= 0)
			{
				System.out.println("No");
				break;
			}
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int H1 = sc.nextInt(); H1 sc.nextInt() sc.nextInt sc int A1 = sc.nextInt(); A1 sc.nextInt() sc.nextInt sc int H2 = sc.nextInt(); H2 sc.nextInt() sc.nextInt sc int A2 = sc.nextInt(); A2 sc.nextInt() sc.nextInt sc while(true)
		{
			H2 -= A1;
			if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			}
			
			H1 -= A2;
			if(H1 <= 0)
			{
				System.out.println("No");
				break;
			}
		} true {
			H2 -= A1;
			if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			}
			
			H1 -= A2;
			if(H1 <= 0)
			{
				System.out.println("No");
				break;
			}
		} H2 -= A1 H2 A1 if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			} H2 <= 0 H2 0 {
				System.out.println("Yes");
				break;
			} System.out.println("Yes") System.out.println System.out System System.out "Yes" break; H1 -= A2 H1 A2 if(H1 <= 0)
			{
				System.out.println("No");
				break;
			} H1 <= 0 H1 0 {
				System.out.println("No");
				break;
			} System.out.println("No") System.out.println System.out System System.out "No" break; String[] args args
import java.util.*;
class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int H1 = sc.nextInt();
		int A1 = sc.nextInt();
		int H2 = sc.nextInt();
		int A2 = sc.nextInt();
		
		while(true)
		{
			H2 -= A1;
			if(H2 <= 0)
			{
				System.out.println("Yes");
				break;
			}
			
			H1 -= A2;
			if(H1 <= 0)
			{
				System.out.println("No");
				break;
			}
		}
	}
}