using System;

public class Program
{
    private const Double C = 299792458d; // Speed of light in vacuum
    private const Double N = 1.000292d; // Index of refraction in air

    private Double elapsedTime = 0.0d;
    private Double distance = 0.0d;

    private static void Main()
    {
        Program prog = new Program();
        prog.Run();

        Console.WriteLine("Press Enter to terminate program");
        Console.ReadLine();
    }

    public Program() { }

    public void Run()
    {
        Console.WriteLine("Speed of light in vacuum: {0}\nIndex of refraction in air (Close to the ground): {1}\n"
            , C, N);

        while (true)
        {
            if (this.ReadInput())
            {
                this.distance = (C * elapsedTime) / (2 * N);

                Console.WriteLine("Result: {0}\n", distance);

                break;
            }
            else
            {
                Console.WriteLine("Invalid input. Please try again\n");
            }
        }
    }

    private Boolean ReadInput()
    {
        Console.WriteLine("Enter elapsed time: ");

        return Double.TryParse(Console.ReadLine(), out this.elapsedTime);
    }
}