import java.util.*;

public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);

        int A = scanner.nextInt();
        int B = scanner.nextInt();
        int C = scanner.nextInt();
        int D = scanner.nextInt();

        while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        }

        String ans;
        if (C <= 0) {ans = "Yes";}
        else {ans = "No";}

        System.out.println(ans);

        scanner.close();
    }
} import java.util.*; util.* java public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);

        int A = scanner.nextInt();
        int B = scanner.nextInt();
        int C = scanner.nextInt();
        int D = scanner.nextInt();

        while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        }

        String ans;
        if (C <= 0) {ans = "Yes";}
        else {ans = "No";}

        System.out.println(ans);

        scanner.close();
    }
} Main public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);

        int A = scanner.nextInt();
        int B = scanner.nextInt();
        int C = scanner.nextInt();
        int D = scanner.nextInt();

        while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        }

        String ans;
        if (C <= 0) {ans = "Yes";}
        else {ans = "No";}

        System.out.println(ans);

        scanner.close();
    } main {
        Scanner scanner = new Scanner(System.in);

        int A = scanner.nextInt();
        int B = scanner.nextInt();
        int C = scanner.nextInt();
        int D = scanner.nextInt();

        while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        }

        String ans;
        if (C <= 0) {ans = "Yes";}
        else {ans = "No";}

        System.out.println(ans);

        scanner.close();
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int A = scanner.nextInt(); A scanner.nextInt() scanner.nextInt scanner int B = scanner.nextInt(); B scanner.nextInt() scanner.nextInt scanner int C = scanner.nextInt(); C scanner.nextInt() scanner.nextInt scanner int D = scanner.nextInt(); D scanner.nextInt() scanner.nextInt scanner while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        } C > 0 && A > 0 C > 0 C 0 A > 0 A 0 {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        } C -= B C B if (C <= 0) {break;} C <= 0 C 0 {break;} break; A -= D A D String ans; ans if (C <= 0) {ans = "Yes";}
        else {ans = "No";} C <= 0 C 0 {ans = "Yes";} ans = "Yes" ans "Yes" {ans = "No";} ans = "No" ans "No" System.out.println(ans) System.out.println System.out System System.out ans scanner.close() scanner.close scanner String[] args args public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);

        int A = scanner.nextInt();
        int B = scanner.nextInt();
        int C = scanner.nextInt();
        int D = scanner.nextInt();

        while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        }

        String ans;
        if (C <= 0) {ans = "Yes";}
        else {ans = "No";}

        System.out.println(ans);

        scanner.close();
    }
} public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);

        int A = scanner.nextInt();
        int B = scanner.nextInt();
        int C = scanner.nextInt();
        int D = scanner.nextInt();

        while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        }

        String ans;
        if (C <= 0) {ans = "Yes";}
        else {ans = "No";}

        System.out.println(ans);

        scanner.close();
    }
} Main
import java.util.*;

public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);

        int A = scanner.nextInt();
        int B = scanner.nextInt();
        int C = scanner.nextInt();
        int D = scanner.nextInt();

        while (C > 0 && A > 0) {
            C -= B;
            if (C <= 0) {break;}
            A -= D;
        }

        String ans;
        if (C <= 0) {ans = "Yes";}
        else {ans = "No";}

        System.out.println(ans);

        scanner.close();
    }
}