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();
    String ans = "No";
    for(int i = 0; i < 200; i++) {
      if((i % 2) == 0) {
        c -= b;
        if(c <= 0) {
          ans = "Yes";
          break;
        }
      } else {
        a -= d;
        if(a <= 0) break;
      }
    }
    System.out.println(ans);
  }
}
/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