import java.util.*;

public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 998244353;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = 200001;


	void doIt() {
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		while(true) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		}
	}

	public static void main(String[] args) {
		new Main().doIt();
	}
} import java.util.*; util.* java public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 998244353;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = 200001;


	void doIt() {
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		while(true) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		}
	}

	public static void main(String[] args) {
		new Main().doIt();
	}
} Main Scanner sc = new Scanner(System.in); sc new Scanner(System.in) final int MOD = 998244353; MOD 998244353 final int MAX = Integer.MAX_VALUE; MAX Integer.MAX_VALUE Integer Integer.MAX_VALUE final long LMAX = Long.MAX_VALUE; LMAX Long.MAX_VALUE Long Long.MAX_VALUE int len = 200001; len 200001 void doIt() {
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		while(true) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		}
	} doIt {
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		while(true) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		}
	} 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) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		} true {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		} 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 if(A <= 0) {
				System.out.println("No");
				return;
			} A <= 0 A 0 {
				System.out.println("No");
				return;
			} System.out.println("No") System.out.println System.out System System.out "No" return; public static void main(String[] args) {
		new Main().doIt();
	} main {
		new Main().doIt();
	} new Main().doIt() new Main().doIt new Main() String[] args args public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 998244353;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = 200001;


	void doIt() {
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		while(true) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		}
	}

	public static void main(String[] args) {
		new Main().doIt();
	}
} public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 998244353;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = 200001;


	void doIt() {
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		while(true) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		}
	}

	public static void main(String[] args) {
		new Main().doIt();
	}
} Main
import java.util.*;

public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 998244353;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = 200001;


	void doIt() {
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int D = sc.nextInt();
		while(true) {
			C -= B;
			if(C <= 0) {
				System.out.println("Yes");
				return;
			}
			A -= D;
			if(A <= 0) {
				System.out.println("No");
				return;
			}
		}
	}

	public static void main(String[] args) {
		new Main().doIt();
	}
}
