//package april2020;

import java.util.*;
import java.lang.*;
import java.math.*;
import java.io.*;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		FastReader scn = new FastReader();
		
		int ht = scn.nextInt();
		int st = scn.nextInt();
		
		int ha = scn.nextInt();
		int sa = scn.nextInt();
		
		int t = 0;
		while(ht>0) {
			ht-=sa;
			t++;
		}
		int a = 0;
		while(ha>0) {
			ha-=st;
			a++;
		}
		if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		}
	}
	static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }

} import java.util.*; util.* java import java.lang.*; lang.* java import java.math.*; math.* java import java.io.*; io.* java public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		FastReader scn = new FastReader();
		
		int ht = scn.nextInt();
		int st = scn.nextInt();
		
		int ha = scn.nextInt();
		int sa = scn.nextInt();
		
		int t = 0;
		while(ht>0) {
			ht-=sa;
			t++;
		}
		int a = 0;
		while(ha>0) {
			ha-=st;
			a++;
		}
		if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		}
	}
	static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }

} Main public static void main(String[] args) {
		// TODO Auto-generated method stub
		FastReader scn = new FastReader();
		
		int ht = scn.nextInt();
		int st = scn.nextInt();
		
		int ha = scn.nextInt();
		int sa = scn.nextInt();
		
		int t = 0;
		while(ht>0) {
			ht-=sa;
			t++;
		}
		int a = 0;
		while(ha>0) {
			ha-=st;
			a++;
		}
		if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		}
	} main {
		// TODO Auto-generated method stub
		FastReader scn = new FastReader();
		
		int ht = scn.nextInt();
		int st = scn.nextInt();
		
		int ha = scn.nextInt();
		int sa = scn.nextInt();
		
		int t = 0;
		while(ht>0) {
			ht-=sa;
			t++;
		}
		int a = 0;
		while(ha>0) {
			ha-=st;
			a++;
		}
		if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		}
	} FastReader scn = new FastReader(); scn new FastReader() int ht = scn.nextInt(); ht scn.nextInt() scn.nextInt scn int st = scn.nextInt(); st scn.nextInt() scn.nextInt scn int ha = scn.nextInt(); ha scn.nextInt() scn.nextInt scn int sa = scn.nextInt(); sa scn.nextInt() scn.nextInt scn int t = 0; t 0 while(ht>0) {
			ht-=sa;
			t++;
		} ht>0 ht 0 {
			ht-=sa;
			t++;
		} ht-=sa ht sa t++ t int a = 0; a 0 while(ha>0) {
			ha-=st;
			a++;
		} ha>0 ha 0 {
			ha-=st;
			a++;
		} ha-=st ha st a++ a if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		} a>t a t {
			System.out.println("No");
		} System.out.println("No") System.out.println System.out System System.out "No" {
			System.out.println("Yes");
		} System.out.println("Yes") System.out.println System.out System System.out "Yes" String[] args args static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    } FastReader BufferedReader br; br StringTokenizer st; st public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } FastReader { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } br = new BufferedReader(new
                     InputStreamReader(System.in)) br new BufferedReader(new
                     InputStreamReader(System.in)) String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } next { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } IOException  e { 
                    e.printStackTrace(); 
                } e.printStackTrace() e.printStackTrace e { 
                    st = new StringTokenizer(br.readLine()); 
                } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } nextInt { 
            return Integer.parseInt(next()); 
        } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nextLong() 
        { 
            return Long.parseLong(next()); 
        } nextLong { 
            return Long.parseLong(next()); 
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } nextDouble { 
            return Double.parseDouble(next()); 
        } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } nextLine { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } String str = ""; str "" try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } catch (IOException e) 
            { 
                e.printStackTrace(); 
            } IOException e { 
                e.printStackTrace(); 
            } e.printStackTrace() e.printStackTrace e { 
                str = br.readLine(); 
            } str = br.readLine() str br.readLine() br.readLine br return str; str public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		FastReader scn = new FastReader();
		
		int ht = scn.nextInt();
		int st = scn.nextInt();
		
		int ha = scn.nextInt();
		int sa = scn.nextInt();
		
		int t = 0;
		while(ht>0) {
			ht-=sa;
			t++;
		}
		int a = 0;
		while(ha>0) {
			ha-=st;
			a++;
		}
		if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		}
	}
	static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }

} public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		FastReader scn = new FastReader();
		
		int ht = scn.nextInt();
		int st = scn.nextInt();
		
		int ha = scn.nextInt();
		int sa = scn.nextInt();
		
		int t = 0;
		while(ht>0) {
			ht-=sa;
			t++;
		}
		int a = 0;
		while(ha>0) {
			ha-=st;
			a++;
		}
		if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		}
	}
	static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }

} Main
//package april2020;

import java.util.*;
import java.lang.*;
import java.math.*;
import java.io.*;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		FastReader scn = new FastReader();
		
		int ht = scn.nextInt();
		int st = scn.nextInt();
		
		int ha = scn.nextInt();
		int sa = scn.nextInt();
		
		int t = 0;
		while(ht>0) {
			ht-=sa;
			t++;
		}
		int a = 0;
		while(ha>0) {
			ha-=st;
			a++;
		}
		if(a>t) {
			System.out.println("No");
		}else {
			System.out.println("Yes");
		}
	}
	static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }

}
