using System;

​

public class Program

{

    static private ulong fact(ulong a,)

    {

        ulong factorial = 1;

        ulong i = 1;

        do

        {

            factorial = factorial * i;

            i++;

        }

        while (i <= a);

        return factorial;

    }

​

    static private ulong nPr(ulong n,ulong r)

    {

        return fact(n) / fact(n-r);

    }

    static private double DectoPer(double a)

    {

        return a * 100;

    }

    static private double PertoDec(double a)

    {

        return a /100;

    }

    static private ulong nCr(ulong n, ulong r)

    {

        return fact (n) / fact(n - r) * fact(r));

    }

    static private float mn(float n1, float n2, float n3, float n4, float n5)

    {

        return (n1 + n2 + n3 + n4 + n5) / 5;

    }

    public static void Main()

    {

        string restart = "chicken nugget";

        while(restart !="q")

        {

            Console.Clear();

            start:

            Console.WriteLine("welcome to the probability calculator.");

            Console.WriteLine("Press 1 for factorial");

            Console.WriteLine("press 2 for permulations");

            Console.WriteLine("3 for decimal to percent");

            Console.WriteLine("4 for percent to decimal");

            Console.WriteLine("5 for combination");

            Console.WriteLine("6 to find the mean for 5 numbers");

        }

        string choice = Console.ReadLine();

            if (choice == "1")

            {

                Console.WriteLine("What number would you like to calculate the factorial of?");

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

                Console.WriteLine(input + "! = " + fact(input));

            }

            else if (choice == "2")

            {

                Console.WriteLine("How many total objects do you have?");

                ulong input1 = ulong.Parse(Console.ReadLine());

                Console.WriteLine("How many objects would you like to arrange?");

                ulong input2 = ulong.Parse(Console.ReadLine());

                Console.WriteLine(input1 + "P" + input2 + "=" + nPr(input1, input2));

            }

        else if (choice == "3")

            {

            Console.WriteLine("What decimal would you like to convert to percent");

            double ans = double.Parse(Console.ReadLine());

            Console.WriteLine(ans + " = " + DectoPer(ans));

        }

        else if choice == "4")

        {

            Console.WriteLine("What decimal would you like to convert to decimal");

            double ans = double.Parse(Console.ReadLine());

            Console.WriteLine(ans + " = " + PertoPer(ans));

        }

        else if choice == "5")

        {

            Console.WriteLine("How many objects do you have in choose?");

            ulong input1 = ulong.Parse(Console.ReadLine());

            Console.WriteLine("How many objects do you have to arrange?");

            ulong input2 = ulong.Parse(Console.ReadLine());

            Console.WriteLine(input1 + "C" + input2 + "=" + nCr(input1, input2));

        }

        else if choice == "6")

        {

            Console.WriteLine("Please enter a number");

        }

        else

        {

            Console.WriteLine("Please enter an number 1 through 6