include <stdio.h>

typedef struct {
	int		hp_max;
	int		hp_cur;
	int		str;
} status;

#define 2 MEMBER

void main()
{
	int i, hp_max1, str1, hp_max2, str2;
	status takahashi, aoki;
	
	scanf("%d %d %d %d", hp_max1, str1, hp_max2, str2);
	
	init(int hp_max1, int str1, int hp_max2, int str2);
	
	do{
		battle();
	}while(takahashi.hp_cur > 0 || aoki.hp_cur > 0)
	
	result();
	
}

void init(int hp_max1, int str1, int hp_max2, int str2)
{
	
	takahashi.hp_max	= hp_max1;
	takahashi.hp_cur	= hp_max1;
	takahashi.str		= str1;
	aoki.hp_max			= hp_max2;
	aoki.hp_cur			= hp_max2;
	aoki.str			= str2;
	
}

void battle()
{
	aoki.hp_cur = aoki.hp_cur - takahashi.str;
	takahashi.hp_cur = takahashi.hp_cur - aoki.atr;
}


void result()
{
	if(aoki.hp_cur <= 0)
	{
		printf("Yes\n");
	} else {
		printf("No\n");
	}
	
}