// Underground problem

using System;

​

namespace ConsoleApp1

{

    class Program

    {

        static string[] Station = { "Brixton", "Stockwell", "Vauxhall", "Pimlico", "Victoria", "Green Park", "Oxford Circus", "Warren Street", "Euston", "King's Cross", "Highbury & Islington", "Finsbury Park", "Seven Sisters", "Tottenham Hale", "Blackhorse Road", "Walthamstow Central" };

        // Function to input a valid station name

        static string GetStation()

        {

            string StationInput = "";

            bool ValidStation = false;

            // Validation

            while (!ValidStation)

            {

                Console.WriteLine("Enter station: ");

                StationInput = Console.ReadLine();

                // Lookup check

                if (Array.IndexOf(Station, StationInput) > -1)

                { ValidStation = true; }

                else

                { Console.WriteLine("Invalid station."); }

            }

            return StationInput;

        }

​

        // Function to calculate the number of stops between two stations

        static int CalculateStops(string StartAt, string StopAt)

        {

            int Stops = 0;

            int Index = 0;

            // Handle the stations being entered in either order

            // Find the first station

            while (Station[Index] != StartAt && Station[Index] != StopAt)

            {

                Index++;

            }

            // Set the next station to be the other station entered

            string NextStation;

            if (Station[Index] == StartAt)

            { NextStation = StopAt; }

            else

            { NextStation = StartAt; }

            // Find the next station counting stops between

            while (Station[Index] != NextStation)

            {

                Index++;

                Stops++;

            }

            return Stops;

        }

​

        // Main program

        static void Main(string[] args)

        {

            string Station1 = GetStation();

            string Station2 = GetStation();

            int Stops = CalculateStops(Station1, Station2);

            Console.WriteLine("{0} to {1} is {2} stops.", Station1, Station2, Stops);

        }

    }

}