import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        abc164_b solver = new abc164_b();
        solver.solve(1, in, out);
        out.close();
    }

    static class abc164_b {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        }

    }
}
 import java.io.OutputStream; OutputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        abc164_b solver = new abc164_b();
        solver.solve(1, in, out);
        out.close();
    }

    static class abc164_b {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        }

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        abc164_b solver = new abc164_b();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        abc164_b solver = new abc164_b();
        solver.solve(1, in, out);
        out.close();
    } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out Scanner in = new Scanner(inputStream); in new Scanner(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) abc164_b solver = new abc164_b(); solver new abc164_b() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class abc164_b {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        }

    } abc164_b public void solve(int testNumber, Scanner in, PrintWriter out) {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        } solve {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        } int A = in.nextInt(); A in.nextInt() in.nextInt in int B = in.nextInt(); B in.nextInt() in.nextInt in int C = in.nextInt(); C in.nextInt() in.nextInt in int D = in.nextInt(); D in.nextInt() in.nextInt in while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            } true {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            } C -= B C B if (C <= 0) {
                    out.println("Yes");
                    return;
                } C <= 0 C 0 {
                    out.println("Yes");
                    return;
                } out.println("Yes") out.println out "Yes" return; A -= D A D if (A <= 0) {
                    out.println("No");
                    return;
                } A <= 0 A 0 {
                    out.println("No");
                    return;
                } out.println("No") out.println out "No" return; int testNumber testNumber Scanner in in PrintWriter out out public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        abc164_b solver = new abc164_b();
        solver.solve(1, in, out);
        out.close();
    }

    static class abc164_b {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        }

    }
} public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        abc164_b solver = new abc164_b();
        solver.solve(1, in, out);
        out.close();
    }

    static class abc164_b {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        abc164_b solver = new abc164_b();
        solver.solve(1, in, out);
        out.close();
    }

    static class abc164_b {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int A = in.nextInt();
            int B = in.nextInt();
            int C = in.nextInt();
            int D = in.nextInt();

            while (true) {
                C -= B;
                if (C <= 0) {
                    out.println("Yes");
                    return;
                }
                A -= D;
                if (A <= 0) {
                    out.println("No");
                    return;
                }

            }


        }

    }
}

