import java.util.*;

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

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