#include <stdbool.h>
#include <stdio.h>

int main(void)
{
	int player_1_hp;
    int player_1_atack;
  	int player_2_hp;
    int player_2_atack;
  	bool in_battle = true;

	scanf("%d %d %d %d",
          &player_1_hp, &player_1_atack,
          &player_2_hp, &player_2_atack);
  	
  	while (in_battle)
  	{
    	player_2_hp -= player_1_atack;
        if (player_2_hp <= 0)
        {
          	in_battle = false;
        }
      	else
        {
			player_1_hp -= player_2_atack;;
            if (player_1_hp <= 0)
            {
                in_battle = false;
            }
        }
  	}

  	if (0 < player_1_hp)
  	{
      	puts("Yes");
  	}
  	else
    {
     	puts("No"); 
    }

  	return 0;
}