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

public class Main {

	static long m = (long) (1e9 + 7);

	public static void main(String[] args) throws IOException {
		Scanner scn = new Scanner(System.in);
		int a[] = { scn.nextInt(), scn.nextInt() };
		int a2[] = { scn.nextInt(), scn.nextInt() };

		int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0);
		int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0);

		if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No");
	}

	static class Scanner {

		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

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

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
	}
} import java.io.*; io.* java import java.util.*; util.* java public class Main {

	static long m = (long) (1e9 + 7);

	public static void main(String[] args) throws IOException {
		Scanner scn = new Scanner(System.in);
		int a[] = { scn.nextInt(), scn.nextInt() };
		int a2[] = { scn.nextInt(), scn.nextInt() };

		int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0);
		int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0);

		if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No");
	}

	static class Scanner {

		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

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

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
	}
} Main static long m = (long) (1e9 + 7); m (long) (1e9 + 7) 1e9 7 public static void main(String[] args) throws IOException {
		Scanner scn = new Scanner(System.in);
		int a[] = { scn.nextInt(), scn.nextInt() };
		int a2[] = { scn.nextInt(), scn.nextInt() };

		int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0);
		int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0);

		if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No");
	} main {
		Scanner scn = new Scanner(System.in);
		int a[] = { scn.nextInt(), scn.nextInt() };
		int a2[] = { scn.nextInt(), scn.nextInt() };

		int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0);
		int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0);

		if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No");
	} Scanner scn = new Scanner(System.in); scn new Scanner(System.in) int a[] = { scn.nextInt(), scn.nextInt() }; a { scn.nextInt(), scn.nextInt() } scn.nextInt() scn.nextInt scn scn.nextInt() scn.nextInt scn int a2[] = { scn.nextInt(), scn.nextInt() }; a2 { scn.nextInt(), scn.nextInt() } scn.nextInt() scn.nextInt scn scn.nextInt() scn.nextInt scn int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0); c1 a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0) a2[0] / a[1] a2[0] a2 0 a[1] a 1 (a2[0] % a[1] != 0 ? 1 : 0) a2[0] % a[1] != 0 a2[0] % a[1] a2[0] a2 0 a[1] a 1 0 1 0 int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0); c2 a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0) a[0] / a2[1] a[0] a 0 a2[1] a2 1 (a[0] % a2[1] != 0 ? 1 : 0) a[0] % a2[1] != 0 a[0] % a2[1] a[0] a 0 a2[1] a2 1 0 1 0 if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No"); c1 <= c2 c1 c2 System.out.println("Yes") System.out.println System.out System System.out "Yes" System.out.println("No") System.out.println System.out System System.out "No" String[] args args static class Scanner {

		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

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

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
	} Scanner StringTokenizer st; st BufferedReader br; br public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		} Scanner {
			br = new BufferedReader(new InputStreamReader(s));
		} br = new BufferedReader(new InputStreamReader(s)) br new BufferedReader(new InputStreamReader(s)) InputStream s s public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		} next {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		} while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine()); st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st public 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 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 class Main {

	static long m = (long) (1e9 + 7);

	public static void main(String[] args) throws IOException {
		Scanner scn = new Scanner(System.in);
		int a[] = { scn.nextInt(), scn.nextInt() };
		int a2[] = { scn.nextInt(), scn.nextInt() };

		int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0);
		int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0);

		if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No");
	}

	static class Scanner {

		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

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

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
	}
} public class Main {

	static long m = (long) (1e9 + 7);

	public static void main(String[] args) throws IOException {
		Scanner scn = new Scanner(System.in);
		int a[] = { scn.nextInt(), scn.nextInt() };
		int a2[] = { scn.nextInt(), scn.nextInt() };

		int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0);
		int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0);

		if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No");
	}

	static class Scanner {

		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

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

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
	}
} Main
import java.io.*;
import java.util.*;

public class Main {

	static long m = (long) (1e9 + 7);

	public static void main(String[] args) throws IOException {
		Scanner scn = new Scanner(System.in);
		int a[] = { scn.nextInt(), scn.nextInt() };
		int a2[] = { scn.nextInt(), scn.nextInt() };

		int c1 = a2[0] / a[1] + (a2[0] % a[1] != 0 ? 1 : 0);
		int c2 = a[0] / a2[1] + (a[0] % a2[1] != 0 ? 1 : 0);

		if (c1 <= c2)
			System.out.println("Yes");
		else
			System.out.println("No");
	}

	static class Scanner {

		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

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

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
	}
}