double dist(double th1, double ph1, double th2, double ph2)
{
	double dx, dy, dz;
	ph1 -= ph2;
	ph1 *= TO_RAD, th1 *= TO_RAD, th2 *= TO_RAD;

	dz = sin(th1) - sin(th2);
	dx = cos(ph1) * cos(th1) - cos(th2);
	dy = sin(ph1) * cos(th1);
	return asin(sqrt(dx * dx + dy * dy + dz * dz) / 2) * 2 * R;
}

int main()
{
	double d = dist(36.12, -86.67, 33.94, -118.4);
	
	printf(, d, d / 1.609344);

	return 0;
}