import java.util.Scanner;

class Main {
    public static void main(String[] args) {
	Scanner stdIn = new Scanner(System.in);

	int a = stdIn.nextInt();
	int b = stdIn.nextInt();
	int c = stdIn.nextInt();
	int d = stdIn.nextInt();


	int deatht = (a % d == 0) ? a/d : a/d+1;
	int deatha = (c % b == 0) ? c/b : c/b+1;

	System.out.println((deatht < deatha) ? "No" : "Yes");
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz