import java .util.Scanner;

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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	}
	if(c<=0) System.out.print("Yes");
	else if(a<=0) System.out.print("No");
    }
} import java .util.Scanner; Scanner 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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	}
	if(c<=0) System.out.print("Yes");
	else if(a<=0) System.out.print("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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	}
	if(c<=0) System.out.print("Yes");
	else if(a<=0) System.out.print("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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	}
	if(c<=0) System.out.print("Yes");
	else if(a<=0) System.out.print("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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	} true {
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    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.print("Yes");
	else if(a<=0) System.out.print("No"); c<=0 c 0 System.out.print("Yes") System.out.print System.out System System.out "Yes" if(a<=0) System.out.print("No"); a<=0 a 0 System.out.print("No") System.out.print 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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	}
	if(c<=0) System.out.print("Yes");
	else if(a<=0) System.out.print("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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	}
	if(c<=0) System.out.print("Yes");
	else if(a<=0) System.out.print("No");
    }
} Main
import java .util.Scanner;

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(true){
	    //高橋の攻撃
	    c -= b;
	    if(c<=0) break;
	    //高橋が攻撃される
	    a -= d;
	    if(a<=0) break;
	}
	if(c<=0) System.out.print("Yes");
	else if(a<=0) System.out.print("No");
    }
}
