/* Yet another variant, from "Carl W.".  No Email address available. */

#include <iostream>
#include <driver.h>

typedef  unsigned long long  Integer;  /* I like sugar */

Integer pi (Integer x)
{
	Integer i, j, k, sum = 2;
	unsigned short int ti, tj;

	if (x<2) return 0;
	if (x<3) return 1;
	if (x<5) return 2;

	for (i = 5, ti = 4; i <= x; i += (ti = 6 - ti), sum += k)
	{
		for (j = 5, tj = 4, k = 1; j * j <= i; j += (tj = 6 - tj))
			if (i % j == 0) { k = 0; break; }
	}

	return sum;
}