using System;

​

public class Program

{

    static private ulong fact(double a)

    {

        ulong factorial = 1;

        ulong i = 1;

        do

        {

            factorial = factorial * i;

            i++;

        }

        while (i <= a);

        return factorial;

    }

​

    static private double pertodec(double a)

    {

        return (a / 100);

    }

​

    static private double dectoper(double a)

    {

        return (a * 100);

    }

​

    static private ulong nPr(double n, double r)

    {

        ulong ans = fact(n) / fact(n - r);

        return ans;

    }

​

    static private ulong nCr(double a, double b)

    {

        ulong ans = fact(a - b) * fact(b);

        ulong combi = fact(a) / ans;

        return combi;

    }

    static private double mean (double a, double b)

    {

    double ans = a/b; 

    return ans;

}

    public static void Main()

    {string restart = "anything";

        while (restart != "q") 

        {

            start:

        Console.WriteLine(" Hello and Welcome to my probability calculator! Please choose an option from the menu ");

        Console.WriteLine(" If you would like to calculate the factorial for a number press 1 ");

        Console.WriteLine(" If you would like to convert from percentage to decimal, press 2");

        Console.WriteLine(" If you would like to convert from decimal to percentage, press 3 ");

        Console.WriteLine(" If you would like to calculate the permutation, press 4");

        Console.WriteLine(" If you would like to calculate the combination, press 5");

        Console.WriteLine(" If you would like to calculate the mean, press 6");

        string input = Console.ReadLine();

        Console.Clear();

        if (input == "1")

        {

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

            double num1 = ulong.Parse(Console.ReadLine());

            Console.WriteLine(" The factorial of " + num1 + " is " + fact(num1));

        }

        else if (input == "2")

        {

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

            double num2 = double.Parse(Console.ReadLine());

            Console.WriteLine(num2 + "% is equal to " + pertodec(num2));

        }

        else if (input == "3")

        {

            Console.WriteLine("Enter the decimal number you would like to convert to percentage ");

            double num3 = double.Parse(Console.ReadLine());

            Console.WriteLine(num3 + " to percentage is  " + dectoper(num3));

        }

        else if (input == "4")

        {

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

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

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

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

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

        }

        else if (input == "5")

        {

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

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

            Console.WriteLine(" How many objects would you like to arranged  if the order does not matter? ");

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

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

        }

        else if (input == "6")

        { 

            Console.WriteLine(" enter the number of values of how many number you want to calculate the mean of  ");

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

        Console.WriteLine(" Please enter the vaules " ) ; 

        double sum = 0; 

        for (int i=1; i<= numb; i++) 

        { double number = double.Parse(Console.ReadLine()); 

         sum += number; 

        } 

        Console.WriteLine(" The mean is " + mean(sum,numb));

        }

            else 

            { Console.WriteLine(" Please enter a correct number from 1-6 from the above options "); 

             Console.WriteLine("    " ); 

              Console.WriteLine("    " ); 

             goto start; 

            }

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

            restart = Console.ReadLine();

    }

​

    }

}