#include <stdio.h>
int main()
{
	int h1,s1,h2,s2;
	scanf("%d %d %d %d",&h1,&s1,&h2,&s2);
	int x,y;
	
	x=h1/s2;
	if(h1%s2!=0) x++;//2攻击次数 
	y=h2/s1;
	if(h2%s1!=0) y++;//1攻击次数 
	
	
	if(x<y) printf("No\n");
	else     printf("Yes\n");
	return 0;
} 