import 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();
        String ans = "No";
        outloop:for(;;){
            c = c-b;
            if(c<=0){
                ans = "Yes";
                break outloop;
            }
            a = a-d;
            if(a<=0){
                break outloop;
            }
        }
        System.out.println(ans);
        }
    } import java.util.*; util.* java 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();
        String ans = "No";
        outloop:for(;;){
            c = c-b;
            if(c<=0){
                ans = "Yes";
                break outloop;
            }
            a = a-d;
            if(a<=0){
                break outloop;
            }
        }
        System.out.println(ans);
        }
    } 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();
        String ans = "No";
        outloop:for(;;){
            c = c-b;
            if(c<=0){
                ans = "Yes";
                break outloop;
            }
            a = a-d;
            if(a<=0){
                break outloop;
            }
        }
        System.out.println(ans);
        } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        String ans = "No";
        outloop:for(;;){
            c = c-b;
            if(c<=0){
                ans = "Yes";
                break outloop;
            }
            a = a-d;
            if(a<=0){
                break outloop;
            }
        }
        System.out.println(ans);
        } 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 String ans = "No"; ans "No" System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import 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();
        String ans = "No";
        outloop:for(;;){
            c = c-b;
            if(c<=0){
                ans = "Yes";
                break outloop;
            }
            a = a-d;
            if(a<=0){
                break outloop;
            }
        }
        System.out.println(ans);
        }
    }
