#!/usr/bin/env python
# -*- coding: utf-8 -*-

from math import atan, cos, sin, sqrt, radians, fabs

class Planet:
	def __init__(self, rad):
		self.radius = rad

class Airport:
	def __init__(self, lat, lon):
		self.latitude = radians(lat)
		self.longitude = radians(lon)

	def countdist(self, airport, planet):
		delta = airport.longitude - self.longitude
		up1 = cos(airport.latitude) * sin(delta)
		up2 = (cos(self.latitude) * sin(airport.latitude)) - (sin(self.latitude) * cos (airport.latitude) * cos(delta))
		up = sqrt(pow(up1, 2) + pow(up2, 2))
		down1 = sin(self.latitude) * sin(airport.latitude)
		down2 = cos(self.latitude) * cos(airport.latitude) * cos (delta)
		down = down1 + down2
		angle = atan(up/down)
		distance = fabs(planet.radius * angle)
		distanceinkm = 1.852 * distance
		print "Distance between two airports is equal to %s nautical miles" % distance
		print " which is %s kilometres" % distanceinkm

if __name__ == "__main__":
	earth = Planet(3440.07)
	airport1 = Airport(float(raw_input("Type in airport 1 latitude in decimal format \n")), float(raw_input("Input airport 1 longitude in decimal format \n")))
	airport2 = Airport(float(raw_input("Type in airport 2 latitude in decimal format \n")), float(raw_input("Input airport 2 longitude in decimal format \n")))
	airport1.countdist(airport2, earth)