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("2 for permuations");

            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 ike to calculate the factorial of?");

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

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

            }

            else if (choice == "2")

            {

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

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

                Console.WriteLine("How many objects do you want 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 + " = " + PertoDec(ans));

            }

            else if (choice == "4")

            {

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

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

                Console.WriteLine(ans + " = " + PertoDec(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 want 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");

                float n1 = float.Parse(Console.ReadLine());

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

                float n2 = float.Parse(Console.ReadLine());

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

                float n3 = float.Parse(Console.ReadLine());

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

                float n4 = float.Parse(Console.ReadLine());

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

                float n5 = float.Parse(Console.ReadLine());

            Console.WriteLine("the mean of the 5 numbers is " + mn(n1, n2, n3, n4, n5));

        }

        else 

        {

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

            goto start;

        }

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

            restart = Console.ReadLine();

        }

    }

}