using System;

public class Program

{

    private static ulong fac(ulong a, ulong num)

    {

        ulong factorial = 1;

    ulong i = 1;

    do

    {num = num * i;

    i++;

    }while(i <= a);

    return factorial;

    }

    private static ulong per(ulong num, ulong a)

    {

    return(num / 100);

    }

    private static double dec(double num)

    {

    return(100 * num);

    }

    private static double 

    {

    return(n / (n-r)!)

    }

    public static void Main()

    {

        string restart = "anything";

        while(restart != "q")

        {

        Console.WriteLine("Hello and Welcome to My Probability Calculator!  Please Choose an option from the menu!");

        Console.WriteLine("If you would like to calculate n!, please press 1." );

        Console.WriteLine("If you would like to calculate nPr, please press 2.");

        Console.WriteLine("If you would like to calculate nCr, please press 3. ");

        Console.WriteLine("If you would like to calculate the mean of a list of numbers, please press 4.");

        Console.WriteLine("If you would like to calculate the median of a list of numbers, please press 5.****");

        Console.WriteLine("If you would like to calculate the mode of a list of numbers, please press 6. ****");

        Console.WriteLine("If you would like to convert a fraction to a decimal, please press 7.");

        ulong i = ulong.Parse(Console.ReadLine());

        Console.Clear();

        if(i == 1)

        {

        ulong a = ulong.Parse(Console.ReadLine());

        ulong num = ulong.Parse(Console.ReadLine());

        Console.WriteLine("n!: " + fac(a , num));

        }

        else if(i == 2)

        {

        ulong a = ulong.Parse(Console.ReadLine());

        Console.WriteLine("Fraction to Decimal: " + dec(a)); 

        }

        else if(i == 3)

        {

        ulong a = ulong.Parse(Console.ReadLine());

        ulong b = ulong.Parse(Console.ReadLine());  

        Console.WriteLine("Permentation: " + per(a ,b));

        }

        else if(i == 4)

        {

        }

        else if(i == 5)

        {

        }

        else if(i == 6)

        {

        }

        else if(i == 7)

        {

        }

        Console.WriteLine("Press q to quit or anything else to continue");

            restart = Console.ReadLine();

            Console.Clear();

        }

    }

}