unsigned int cbpi2(unsigned int x)
{
	unsigned int i,j,k,idx,jdx,sum;
	static unsigned int skip[] = {4,2,4,2,4,6,2,6};

	if (x < 7) return(8*x+2)/13;

	idx = 0;
	for (i=7,sum=3;i <= x;i+=skip[idx++],sum += k)
	{
		idx &= 7;
		jdx = 0;
		for (j=7,k=1;j*j <= i;j += skip[jdx++])
		{
			jdx &= 7;
			if (i % j) continue;
			else
			{
				k = 0;
				break;
			}
		}
	}
	return sum;
}

unsigned long long pi(unsigned long long x) { return cbpi2(x); }