import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int thp = sc.nextInt();
        int tk = sc.nextInt();
		int ahp = sc.nextInt();
        int ak = sc.nextInt();
      
            String result = "";
      
      for(int i=0; i<100; i++){
        ahp = ahp - tk;
        
       if(ahp <= 0){
        result = "Yes";
        break;
       }
              
      	thp = thp - ak;
      
      if(thp <= 0){
        result = "No";
        break;
      }
      
      }
		// 文字列の入力
		System.out.println(result);
	}
}
/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