#include<stdio.h>

int main(){
  int t_hp,t_a,a_hp,a_a;
  int t_c,a_c;
  if(scanf("%d%d",&t_hp,&t_a,&a_hp,&a_a)!=4) return -1;
  t_c=t_hp/a_a; 
  a_c=a_hp/t_a; 
  if(t_hp%a_a!=0) {
  	t_c++; 
  }
  if(a_hp%t_a!=0) {
  	a_c++; 
  }
  if(t_c>=a_c) printf("Yes\n");
  else printf("No\n");
  return 0;
}