import java.util.*;


		       public class Main {

		           public static void main(String args[])  {
		        	   Scanner sc =new Scanner(System.in);
		        	   int lifeA = sc.nextInt();
		        	   int attackA = sc.nextInt();
		        	   int lifeB = sc.nextInt();
		        	   int attackB = sc.nextInt();	
                      while(lifeA>0 && lifeB>0) {
                    	  if(lifeA>0) {
                    		  lifeB -= attackA;
                    	  }
                    	  if(lifeB>0){
                    		  lifeA -=attackB;
                    	  }

                      }
                      if(lifeA <lifeB) {
                    	  System.out.println("No");
                      }else {
                    	  System.out.println("Yes");
                      }

		           }
		       }



/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