#include <stdio.h>
#include <algorithm>
using namespace std;

long long l, r, m, k;

int main()
{
	scanf ("%lld %lld %lld %lld", &l, &r, &m, &k);
	l *= k; r *= k;

	puts((l + m - 1) / m <= r / m ? "Yes" : "No");
	return 0;
}