import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a1 = scan.nextInt();
    int a2 = scan.nextInt();
    int b1 = scan.nextInt();
    int b2 = scan.nextInt();
    while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    }
    if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  }
} import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a1 = scan.nextInt();
    int a2 = scan.nextInt();
    int b1 = scan.nextInt();
    int b2 = scan.nextInt();
    while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    }
    if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  }
} Main public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a1 = scan.nextInt();
    int a2 = scan.nextInt();
    int b1 = scan.nextInt();
    int b2 = scan.nextInt();
    while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    }
    if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  } main {
    Scanner scan = new Scanner(System.in);
    int a1 = scan.nextInt();
    int a2 = scan.nextInt();
    int b1 = scan.nextInt();
    int b2 = scan.nextInt();
    while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    }
    if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int a1 = scan.nextInt(); a1 scan.nextInt() scan.nextInt scan int a2 = scan.nextInt(); a2 scan.nextInt() scan.nextInt scan int b1 = scan.nextInt(); b1 scan.nextInt() scan.nextInt scan int b2 = scan.nextInt(); b2 scan.nextInt() scan.nextInt scan while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    } (b1>0)&&(a1>0) (b1>0) b1 0 (a1>0) a1 0 {
      b1-=a2;
      a1-=b2;
    } b1-=a2 b1 a2 a1-=b2 a1 b2 if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    } b1<=0 b1 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" String[] args args public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a1 = scan.nextInt();
    int a2 = scan.nextInt();
    int b1 = scan.nextInt();
    int b2 = scan.nextInt();
    while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    }
    if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  }
} public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a1 = scan.nextInt();
    int a2 = scan.nextInt();
    int b1 = scan.nextInt();
    int b2 = scan.nextInt();
    while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    }
    if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  }
} Main
import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a1 = scan.nextInt();
    int a2 = scan.nextInt();
    int b1 = scan.nextInt();
    int b2 = scan.nextInt();
    while ((b1>0)&&(a1>0)){
      b1-=a2;
      a1-=b2;
    }
    if (b1<=0){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  }
}
