import java.util.Scanner;

public class Main{
  public static void main(String[] args){
    Scanner scanner = new Scanner(System.in);
    int A = scanner.nextInt();
    int B = scanner.nextInt();
    int C = scanner.nextInt();
    int D = scanner.nextInt();
    
    System.out.println(cal(A,D) >= cal(C,B) ? "Yes" : "No");
  }
  
  private static int cal(int a,int b){
    int i;
    for(i = 0;a - b > 0;i++){
      a = a - b;
    }
    return i;
  }
}
/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