factorial.cs

using System.Numerics;

namespace FactorialExample;

internal static class Program
{
    
    private static BigInteger Factorial(int number) {
        if (number == 0) return 1;

        return number * Factorial(number - 1);
    }

    private static void Main(string[] args)
    {
        Console.Write("Please enter a number greater than zero: ");
        if(!int.TryParse(Console.ReadLine(), out int number))
        {
            Console.WriteLine("Not a valid number!");
            return;
        }

        BigInteger factorial = Factorial(number);

        Console.WriteLine($"The Factorial of {number} is {factorial}.");
    }
}