import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        int T_time = (A-1)/D+1;
        int A_time = (C-1)/B+1;

        
        if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes");
        

	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        int T_time = (A-1)/D+1;
        int A_time = (C-1)/B+1;

        
        if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes");
        

	}
} Main public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        int T_time = (A-1)/D+1;
        int A_time = (C-1)/B+1;

        
        if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes");
        

	} main {
		// TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        int T_time = (A-1)/D+1;
        int A_time = (C-1)/B+1;

        
        if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes");
        

	} 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 int T_time = (A-1)/D+1; T_time (A-1)/D+1 (A-1)/D (A-1) A 1 D 1 int A_time = (C-1)/B+1; A_time (C-1)/B+1 (C-1)/B (C-1) C 1 B 1 if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes"); T_time < A_time T_time A_time System.out.println("No") System.out.println System.out System System.out "No" System.out.println("Yes") System.out.println System.out System System.out "Yes" String[] args args public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        int T_time = (A-1)/D+1;
        int A_time = (C-1)/B+1;

        
        if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes");
        

	}
} public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        int T_time = (A-1)/D+1;
        int A_time = (C-1)/B+1;

        
        if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes");
        

	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        int T_time = (A-1)/D+1;
        int A_time = (C-1)/B+1;

        
        if (T_time < A_time)
        	System.out.println("No");
        else
        	System.out.println("Yes");
        

	}
}
