import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        }
    }
    public static int Attack(int H, int A){
        H -= A;
        return H;
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        }
    }
    public static int Attack(int H, int A){
        H -= A;
        return H;
    }
} Main public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        }
    } main {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        }
    } 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 for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        } ; {
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        } {
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        } C = Attack(C,B) C Attack(C,B) Attack C B if(C<=0){
                System.out.println("Yes");
                break;
            } C<=0 C 0 {
                System.out.println("Yes");
                break;
            } System.out.println("Yes") System.out.println System.out System System.out "Yes" break; A = Attack(A,D) A Attack(A,D) Attack A D if(A<=0){
                System.out.println("No");
                break;
            } A<=0 A 0 {
                System.out.println("No");
                break;
            } System.out.println("No") System.out.println System.out System System.out "No" break; String[] args args public static int Attack(int H, int A){
        H -= A;
        return H;
    } Attack {
        H -= A;
        return H;
    } H -= A H A return H; H int H H int A A public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        }
    }
    public static int Attack(int H, int A){
        H -= A;
        return H;
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        }
    }
    public static int Attack(int H, int A){
        H -= A;
        return H;
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int C = sc.nextInt();
        int D = sc.nextInt();
        
        for(;;){
            C = Attack(C,B);
            if(C<=0){
                System.out.println("Yes");
                break;
            }
            A = Attack(A,D);
            if(A<=0){
                System.out.println("No");
                break;
            }
        }
    }
    public static int Attack(int H, int A){
        H -= A;
        return H;
    }
}
