import java.util.*;
public class Main {
	public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      //取得
      int A = sc.nextInt();
      int B = sc.nextInt();
      int C = sc.nextInt();
      int D = sc.nextInt();
      int i = 1;
      //どちらかが体力なくなるまで対戦
      //奇数回は高橋の攻撃
      while(A>0 && C>0){
        if(i%2==1){
          C-=B;
        }else{
          A-=D;
        }
        i++;
      }
      //高モンの体力は？
      if(A>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