import 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();

    boolean takahashi = true;

    while (a > 0 && c > 0) {
      if (takahashi) {
        c -= b;
      } else {
        a -= d;
      }
      takahashi = !takahashi;
    }

    if (c <= 0) {
      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