function fD(a, b, c) {
	for (; a > c;)
		a -= c - b;
	for (; a < b;)
		a += c - b;
	return a;
};
function jD(a, b, c) {
	b != null && (a = Math.max(a, b));
	c != null && (a = Math.min(a, c));
	return a;
};
function yk(a) {
	return Math.PI * a / 180
};
function Ce(a, b, c, d) {
	var dO = 6370996.81;
	return dO * Math.acos(Math.sin(c) * Math.sin(d) + Math.cos(c) * Math.cos(d) * Math.cos(b - a));
};
function getDistance(a, b) {
	if (!a || !b)
		return 0;
	a.lng = fD(a.lng, -180, 180);
	a.lat = jD(a.lat, -74, 74);
	b.lng = fD(b.lng, -180, 180);
	b.lat = jD(b.lat, -74, 74);
	return Ce(yk(a.lng), yk(b.lng), yk(a.lat), yk(b.lat));
};

alert(getDistance({lng : 106.486654, lat: 29.490295},{lng : 106.581515,lat :29.615467}));