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