import java.util.Scanner;

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

    int A = scanner.nextInt();
    int B = scanner.nextInt();
    int C = scanner.nextInt();
    int D = scanner.nextInt();
    if ((A + D - 1) / D >= (C + B - 1) / B) System.out.println("Yes");
    else {
      System.out.println("No");
    }
  }
}

/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