import java.util.*;
import java.lang.*;

public class Main{

    public static void solve(long a , long b,long c , long d){//healt , str
        while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        }

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

    public static void gora(){
        Scanner scn = new Scanner(System.in);

        // long test = scn.nextLong();

        long a = scn.nextLong();

        long b = scn.nextLong();


        long c = scn.nextLong();

        long d = scn.nextLong();
        // long arr[] = new long[n];

        // for(int i = 0 ; i < arr.length ; i++){
        //     arr[i] = scn.nextLong();
        // }

        solve(a,b,c,d );
    }

    public static void main(String args[]){
        gora();
    }
}

 import java.util.*; util.* java import java.lang.*; lang.* java public class Main{

    public static void solve(long a , long b,long c , long d){//healt , str
        while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        }

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

    public static void gora(){
        Scanner scn = new Scanner(System.in);

        // long test = scn.nextLong();

        long a = scn.nextLong();

        long b = scn.nextLong();


        long c = scn.nextLong();

        long d = scn.nextLong();
        // long arr[] = new long[n];

        // for(int i = 0 ; i < arr.length ; i++){
        //     arr[i] = scn.nextLong();
        // }

        solve(a,b,c,d );
    }

    public static void main(String args[]){
        gora();
    }
} Main public static void solve(long a , long b,long c , long d){//healt , str
        while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        }

        if(c == 0){
                System.out.println("Yes");
        }else{
            System.out.println("No");
        }
    } solve {//healt , str
        while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        }

        if(c == 0){
                System.out.println("Yes");
        }else{
            System.out.println("No");
        }
    } while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        } a > 0 && c > 0 a > 0 a 0 c > 0 c 0 {
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        } c -= b c b if(c <= 0){
                System.out.println("Yes");
                return;
            } c <= 0 c 0 {
                System.out.println("Yes");
                return;
            } System.out.println("Yes") System.out.println System.out System System.out "Yes" return; a -= d a d if(c == 0){
                System.out.println("Yes");
        }else{
            System.out.println("No");
        } c == 0 c 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" long a a long b b long c c long d d public static void gora(){
        Scanner scn = new Scanner(System.in);

        // long test = scn.nextLong();

        long a = scn.nextLong();

        long b = scn.nextLong();


        long c = scn.nextLong();

        long d = scn.nextLong();
        // long arr[] = new long[n];

        // for(int i = 0 ; i < arr.length ; i++){
        //     arr[i] = scn.nextLong();
        // }

        solve(a,b,c,d );
    } gora {
        Scanner scn = new Scanner(System.in);

        // long test = scn.nextLong();

        long a = scn.nextLong();

        long b = scn.nextLong();


        long c = scn.nextLong();

        long d = scn.nextLong();
        // long arr[] = new long[n];

        // for(int i = 0 ; i < arr.length ; i++){
        //     arr[i] = scn.nextLong();
        // }

        solve(a,b,c,d );
    } Scanner scn = new Scanner(System.in); scn new Scanner(System.in) long a = scn.nextLong(); a scn.nextLong() scn.nextLong scn long b = scn.nextLong(); b scn.nextLong() scn.nextLong scn long c = scn.nextLong(); c scn.nextLong() scn.nextLong scn long d = scn.nextLong(); d scn.nextLong() scn.nextLong scn solve(a,b,c,d ) solve a b c d public static void main(String args[]){
        gora();
    } main {
        gora();
    } gora() gora String args[] args public class Main{

    public static void solve(long a , long b,long c , long d){//healt , str
        while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        }

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

    public static void gora(){
        Scanner scn = new Scanner(System.in);

        // long test = scn.nextLong();

        long a = scn.nextLong();

        long b = scn.nextLong();


        long c = scn.nextLong();

        long d = scn.nextLong();
        // long arr[] = new long[n];

        // for(int i = 0 ; i < arr.length ; i++){
        //     arr[i] = scn.nextLong();
        // }

        solve(a,b,c,d );
    }

    public static void main(String args[]){
        gora();
    }
} public class Main{

    public static void solve(long a , long b,long c , long d){//healt , str
        while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        }

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

    public static void gora(){
        Scanner scn = new Scanner(System.in);

        // long test = scn.nextLong();

        long a = scn.nextLong();

        long b = scn.nextLong();


        long c = scn.nextLong();

        long d = scn.nextLong();
        // long arr[] = new long[n];

        // for(int i = 0 ; i < arr.length ; i++){
        //     arr[i] = scn.nextLong();
        // }

        solve(a,b,c,d );
    }

    public static void main(String args[]){
        gora();
    }
} Main
import java.util.*;
import java.lang.*;

public class Main{

    public static void solve(long a , long b,long c , long d){//healt , str
        while(a > 0 && c > 0){
            c -= b;
            if(c <= 0){
                System.out.println("Yes");
                return;
            }
            a -= d;
        }

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

    public static void gora(){
        Scanner scn = new Scanner(System.in);

        // long test = scn.nextLong();

        long a = scn.nextLong();

        long b = scn.nextLong();


        long c = scn.nextLong();

        long d = scn.nextLong();
        // long arr[] = new long[n];

        // for(int i = 0 ; i < arr.length ; i++){
        //     arr[i] = scn.nextLong();
        // }

        solve(a,b,c,d );
    }

    public static void main(String args[]){
        gora();
    }
}


