import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();

		sc.close();
		
		String result = null;
		while (result == null) {
			C -= B;
			if (C <= 0) {
				result = "Yes";
				break;
			}
			A -= D;
			if (A <= 0) {
				result = "No";
			}
		}
		System.out.println(result);
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();

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

		sc.close();
		
		String result = null;
		while (result == null) {
			C -= B;
			if (C <= 0) {
				result = "Yes";
				break;
			}
			A -= D;
			if (A <= 0) {
				result = "No";
			}
		}
		System.out.println(result);
	} main {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();

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

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

		sc.close();
		
		String result = null;
		while (result == null) {
			C -= B;
			if (C <= 0) {
				result = "Yes";
				break;
			}
			A -= D;
			if (A <= 0) {
				result = "No";
			}
		}
		System.out.println(result);
	}
} Main
import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();

		sc.close();
		
		String result = null;
		while (result == null) {
			C -= B;
			if (C <= 0) {
				result = "Yes";
				break;
			}
			A -= D;
			if (A <= 0) {
				result = "No";
			}
		}
		System.out.println(result);
	}
}