#include <stdio.h>

int main()
{
	int a, b, c, d;
	scanf("%d %d %d %d", &a, &b, &c, &d);
	int e, f;
	e = a / c;
	f = b / d;
	(a % c) ? e++ : e;
	(b % d) ? f++ : f;
	(f >= e) ? printf("No") : printf("Yes");
	return 0;
}