import java.util.Scanner;

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();
        for(int i=0;i<10000000;i++)
        {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        }


    }
} import java.util.Scanner; Scanner java.util 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();
        for(int i=0;i<10000000;i++)
        {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        }


    }
} 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();
        for(int i=0;i<10000000;i++)
        {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        }


    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        for(int i=0;i<10000000;i++)
        {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        }


    } 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 for(int i=0;i<10000000;i++)
        {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        } int i=0; int i=0; i 0 i<10000000 i 10000000 i++ i++ i {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        } {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        } c = c-b c c-b c b a = a-d a a-d a d if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            } c<=0 c 0 {
                System.out.print("Yes");
                break;
            } System.out.print("Yes") System.out.print System.out System System.out "Yes" break; if(a<=0)
            {
                System.out.print("No");
                break;
            } a<=0 a 0 {
                System.out.print("No");
                break;
            } System.out.print("No") System.out.print System.out System System.out "No" break; String args[] args
import java.util.Scanner;

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();
        for(int i=0;i<10000000;i++)
        {
            c = c-b;
            a = a-d;
            if(c<=0)
            {
                System.out.print("Yes");
                break;
            }
            else if(a<=0)
            {
                System.out.print("No");
                break;
            }
        }


    }
}