import java.math.*;
import java.util.*;


public class Main {

    public static void main(String args[]){
        Scanner scan =new Scanner(System.in);
        int Th =scan.nextInt();
        int Ts=scan.nextInt();
        int Ah =scan.nextInt();
        int As=scan.nextInt();
        int i=0;
        while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        }
        if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        }
    }

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

    public static void main(String args[]){
        Scanner scan =new Scanner(System.in);
        int Th =scan.nextInt();
        int Ts=scan.nextInt();
        int Ah =scan.nextInt();
        int As=scan.nextInt();
        int i=0;
        while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        }
        if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        }
    }

} Main public static void main(String args[]){
        Scanner scan =new Scanner(System.in);
        int Th =scan.nextInt();
        int Ts=scan.nextInt();
        int Ah =scan.nextInt();
        int As=scan.nextInt();
        int i=0;
        while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        }
        if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        }
    } main {
        Scanner scan =new Scanner(System.in);
        int Th =scan.nextInt();
        int Ts=scan.nextInt();
        int Ah =scan.nextInt();
        int As=scan.nextInt();
        int i=0;
        while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        }
        if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        }
    } Scanner scan =new Scanner(System.in); scan new Scanner(System.in) int Th =scan.nextInt(); Th scan.nextInt() scan.nextInt scan int Ts=scan.nextInt(); Ts scan.nextInt() scan.nextInt scan int Ah =scan.nextInt(); Ah scan.nextInt() scan.nextInt scan int As=scan.nextInt(); As scan.nextInt() scan.nextInt scan int i=0; i 0 while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        } Th>0 && Ah>0 Th>0 Th 0 Ah>0 Ah 0 {
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        } if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            } i%2==0 i%2 i 2 0 {
                Ah=Ah-Ts;
            } Ah=Ah-Ts Ah Ah-Ts Ah Ts if(i%2==1){
                Th=Th-As;
            } i%2==1 i%2 i 2 1 {
                Th=Th-As;
            } Th=Th-As Th Th-As Th As i++ i if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        } Ah<=0 Ah 0 {
            System.out.print("Yes");
        } System.out.print("Yes") System.out.print System.out System System.out "Yes" if(Th<=0){
            System.out.println("No");
        } Th<=0 Th 0 {
            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 Th =scan.nextInt();
        int Ts=scan.nextInt();
        int Ah =scan.nextInt();
        int As=scan.nextInt();
        int i=0;
        while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        }
        if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        }
    }

} public class Main {

    public static void main(String args[]){
        Scanner scan =new Scanner(System.in);
        int Th =scan.nextInt();
        int Ts=scan.nextInt();
        int Ah =scan.nextInt();
        int As=scan.nextInt();
        int i=0;
        while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        }
        if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        }
    }

} Main
import java.math.*;
import java.util.*;


public class Main {

    public static void main(String args[]){
        Scanner scan =new Scanner(System.in);
        int Th =scan.nextInt();
        int Ts=scan.nextInt();
        int Ah =scan.nextInt();
        int As=scan.nextInt();
        int i=0;
        while(Th>0 && Ah>0){
            
            if(i%2==0){
                Ah=Ah-Ts;
            }
            else if(i%2==1){
                Th=Th-As;
            }
           
            i++;
        }
        if(Ah<=0){
            System.out.print("Yes");
        }
        else if(Th<=0){
            System.out.println("No");
        }
    }

}
