import java.util.*;
import java.io.*;

public class Main{
  public static void main(String[] args)throws Exception{
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int D = sc.nextInt();
    
    int X = (B+C-1)/B;
    int Y = (A+D-1)/D;
    System.out.println(X<=Y ? "Yes" : "No");
  }
} import java.util.*; util.* java import java.io.*; io.* java public class Main{
  public static void main(String[] args)throws Exception{
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int D = sc.nextInt();
    
    int X = (B+C-1)/B;
    int Y = (A+D-1)/D;
    System.out.println(X<=Y ? "Yes" : "No");
  }
} Main public static void main(String[] args)throws Exception{
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int D = sc.nextInt();
    
    int X = (B+C-1)/B;
    int Y = (A+D-1)/D;
    System.out.println(X<=Y ? "Yes" : "No");
  } main {
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int D = sc.nextInt();
    
    int X = (B+C-1)/B;
    int Y = (A+D-1)/D;
    System.out.println(X<=Y ? "Yes" : "No");
  } 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 int X = (B+C-1)/B; X (B+C-1)/B (B+C-1) B+C B C 1 B int Y = (A+D-1)/D; Y (A+D-1)/D (A+D-1) A+D A D 1 D System.out.println(X<=Y ? "Yes" : "No") System.out.println System.out System System.out X<=Y ? "Yes" : "No" X<=Y X Y "Yes" "No" String[] args args public class Main{
  public static void main(String[] args)throws Exception{
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int D = sc.nextInt();
    
    int X = (B+C-1)/B;
    int Y = (A+D-1)/D;
    System.out.println(X<=Y ? "Yes" : "No");
  }
} public class Main{
  public static void main(String[] args)throws Exception{
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int D = sc.nextInt();
    
    int X = (B+C-1)/B;
    int Y = (A+D-1)/D;
    System.out.println(X<=Y ? "Yes" : "No");
  }
} Main
import java.util.*;
import java.io.*;

public class Main{
  public static void main(String[] args)throws Exception{
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int D = sc.nextInt();
    
    int X = (B+C-1)/B;
    int Y = (A+D-1)/D;
    System.out.println(X<=Y ? "Yes" : "No");
  }
}