import java.util.*;
public class Main {
    public static void main(String[] args) {
        int a=0;
        int b=0;
        int c=0;
        int d=0;
        Scanner scan = new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        c=scan.nextInt();
        d=scan.nextInt();
        while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        }


    }


}
 import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        int a=0;
        int b=0;
        int c=0;
        int d=0;
        Scanner scan = new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        c=scan.nextInt();
        d=scan.nextInt();
        while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        }


    }


} Main public static void main(String[] args) {
        int a=0;
        int b=0;
        int c=0;
        int d=0;
        Scanner scan = new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        c=scan.nextInt();
        d=scan.nextInt();
        while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        }


    } main {
        int a=0;
        int b=0;
        int c=0;
        int d=0;
        Scanner scan = new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        c=scan.nextInt();
        d=scan.nextInt();
        while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        }


    } int a=0; a 0 int b=0; b 0 int c=0; c 0 int d=0; d 0 Scanner scan = new Scanner(System.in); scan new Scanner(System.in) a=scan.nextInt() a scan.nextInt() scan.nextInt scan b=scan.nextInt() b scan.nextInt() scan.nextInt scan c=scan.nextInt() c scan.nextInt() scan.nextInt scan d=scan.nextInt() d scan.nextInt() scan.nextInt scan while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        } true {
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        } c=c-b c c-b c b a=a-d a a-d a d if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            } c<=0 c 0 {
                System.out.println("Yes");
                break;
            } System.out.println("Yes") System.out.println System.out System System.out "Yes" break; if(a<=0){
                System.out.println("No");
                break;
            } a<=0 a 0 {
                System.out.println("No");
                break;
            } System.out.println("No") System.out.println System.out System System.out "No" break; String[] args args public class Main {
    public static void main(String[] args) {
        int a=0;
        int b=0;
        int c=0;
        int d=0;
        Scanner scan = new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        c=scan.nextInt();
        d=scan.nextInt();
        while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        }


    }


} public class Main {
    public static void main(String[] args) {
        int a=0;
        int b=0;
        int c=0;
        int d=0;
        Scanner scan = new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        c=scan.nextInt();
        d=scan.nextInt();
        while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        }


    }


} Main
import java.util.*;
public class Main {
    public static void main(String[] args) {
        int a=0;
        int b=0;
        int c=0;
        int d=0;
        Scanner scan = new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        c=scan.nextInt();
        d=scan.nextInt();
        while (true){
            c=c-b;
            a=a-d;
            //System.out.println("aoki:="+c);
            //System.out.println("takahasi:="+a);
            //System.out.println("  ");






            if(c<=0){
                System.out.println("Yes");
                break;
            }
            else if(a<=0){
                System.out.println("No");
                break;
            }

        }


    }


}

