import java.util.*;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int tkMonsterHp = sc.nextInt();
    int tkMonsterAttack = sc.nextInt();
    int aoMonsterHp = sc.nextInt();
    int aoMonsterAttack = sc.nextInt();

    while (tkMonsterHp > 0 && aoMonsterHp > 0) {
      aoMonsterHp -= tkMonsterAttack;
      if(aoMonsterHp <= 0) {
        System.out.println("Yes");
        break;
      }

      tkMonsterHp -= aoMonsterAttack;

      if(tkMonsterHp <= 0) {
        System.out.println("No");
        break;
      }
      
    }
    sc.close();
  }
}
/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