calculating factorials in C#
<p>I am trying to write a program that will take the users input value and asks whether they want to calculate the value of the numbers 1 to n or the factorial of n!
This is what I have so far</p>

<pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Project_2_Part_B
{
    class Program
    {
        static void Main(string[] args)
        {                
             var Fkeylow = "f";
             var FkeyCap = "F";
             var Skeylow="s";
             var SkeyCap="S";
             int n = 0;
             long factorial = n;

             Console.WriteLine("Input a value n");
             n = Convert.ToInt32(Console.ReadLine());

             Console.WriteLine("Do you want to calculate factorial or sum");
             Console.WriteLine("Enter F or S");

             var A = Console.ReadLine();

             if (A == Fkeylow)
                 Console.WriteLine();

             if (A == FkeyCap)
                 Console.WriteLine();

             var B=Console.ReadLine();

             if (B == Skeylow)
                 Console.WriteLine();

             if (B == SkeyCap)
                 Console.WriteLine();

             Console.WriteLine("Press any key to close...");
             Console.ReadLine();
         }
     }
}
</code></pre>

<p>My issue is with the syntax of the calculation to make the code execute the n*(n-1) while n>1
Any help would be greatly appreciated. Thank you in advanced!</p>
