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

public class Main {
    static StringTokenizer st;
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws IOException {
        int health1 = nextInt();
        int attack1 = nextInt();
        int health2 = nextInt();
        int attack2 = nextInt();
        while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        }
        if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        }
    }
    
    public static int nextInt() throws IOException {
        return Integer.parseInt(next());
    }
    public static long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    public static double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    static String next() throws IOException {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim());
        return st.nextToken();
    }
}

 import java.util.*; util.* java import java.io.*; io.* java public class Main {
    static StringTokenizer st;
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws IOException {
        int health1 = nextInt();
        int attack1 = nextInt();
        int health2 = nextInt();
        int attack2 = nextInt();
        while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        }
        if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        }
    }
    
    public static int nextInt() throws IOException {
        return Integer.parseInt(next());
    }
    public static long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    public static double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    static String next() throws IOException {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim());
        return st.nextToken();
    }
} Main static StringTokenizer st; st static BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) public static void main(String[] args) throws IOException {
        int health1 = nextInt();
        int attack1 = nextInt();
        int health2 = nextInt();
        int attack2 = nextInt();
        while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        }
        if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        }
    } main {
        int health1 = nextInt();
        int attack1 = nextInt();
        int health2 = nextInt();
        int attack2 = nextInt();
        while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        }
        if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        }
    } int health1 = nextInt(); health1 nextInt() nextInt int attack1 = nextInt(); attack1 nextInt() nextInt int health2 = nextInt(); health2 nextInt() nextInt int attack2 = nextInt(); attack2 nextInt() nextInt while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        } health1>0 && health2>0 health1>0 health1 0 health2>0 health2 0 {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        } health2-=attack1 health2 attack1 if (health2<=0) {
                System.out.println("Yes");
                return;
            } health2<=0 health2 0 {
                System.out.println("Yes");
                return;
            } System.out.println("Yes") System.out.println System.out System System.out "Yes" return; health1-=attack2 health1 attack2 if (health1<=0) {
                System.out.println("No");
                return;
            } health1<=0 health1 0 {
                System.out.println("No");
                return;
            } System.out.println("No") System.out.println System.out System System.out "No" return; if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        } health1<=0 health1 0 { //reee captialization
            System.out.println("No");
        } System.out.println("No") System.out.println System.out System System.out "No" if (health2<=0) {
            System.out.println("Yes");
        } health2<=0 health2 0 {
            System.out.println("Yes");
        } System.out.println("Yes") System.out.println System.out System System.out "Yes" String[] args args public static int nextInt() throws IOException {
        return Integer.parseInt(next());
    } nextInt {
        return Integer.parseInt(next());
    } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next public static long nextLong() throws IOException {
        return Long.parseLong(next());
    } nextLong {
        return Long.parseLong(next());
    } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public static double nextDouble() throws IOException {
        return Double.parseDouble(next());
    } nextDouble {
        return Double.parseDouble(next());
    } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next static String next() throws IOException {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim());
        return st.nextToken();
    } next {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim());
        return st.nextToken();
    } while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim()); st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st st = new StringTokenizer(br.readLine().trim()) st new StringTokenizer(br.readLine().trim()) return st.nextToken(); st.nextToken() st.nextToken st public class Main {
    static StringTokenizer st;
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws IOException {
        int health1 = nextInt();
        int attack1 = nextInt();
        int health2 = nextInt();
        int attack2 = nextInt();
        while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        }
        if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        }
    }
    
    public static int nextInt() throws IOException {
        return Integer.parseInt(next());
    }
    public static long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    public static double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    static String next() throws IOException {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim());
        return st.nextToken();
    }
} public class Main {
    static StringTokenizer st;
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws IOException {
        int health1 = nextInt();
        int attack1 = nextInt();
        int health2 = nextInt();
        int attack2 = nextInt();
        while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        }
        if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        }
    }
    
    public static int nextInt() throws IOException {
        return Integer.parseInt(next());
    }
    public static long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    public static double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    static String next() throws IOException {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim());
        return st.nextToken();
    }
} Main
import java.util.*;
import java.io.*;

public class Main {
    static StringTokenizer st;
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws IOException {
        int health1 = nextInt();
        int attack1 = nextInt();
        int health2 = nextInt();
        int attack2 = nextInt();
        while (health1>0 && health2>0) {
            health2-=attack1;
            if (health2<=0) {
                System.out.println("Yes");
                return;
            }
            health1-=attack2;
            if (health1<=0) {
                System.out.println("No");
                return;
            }
        }
        if (health1<=0) { //reee captialization
            System.out.println("No");
        }
        else if (health2<=0) {
            System.out.println("Yes");
        }
    }
    
    public static int nextInt() throws IOException {
        return Integer.parseInt(next());
    }
    public static long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    public static double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    static String next() throws IOException {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine().trim());
        return st.nextToken();
    }
}


