/******************************************************/
/* Introduction to Programming                        */
/* By Dr. ANTF                                        */
/* www.antf.net                                       */
/* Copyright 2015                                     */
/*                                                    */
/* C# 319 - Problem 18: Summation 2 (b)               */
/******************************************************/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DOS
{
    class Program
    {
        static void Main(string[] args)
        {
            int n, factorial;
            float sum = 0f;

            Console.Write("Please enter a number: ");
            n = int.Parse(Console.ReadLine());

            for (int i = 1; i <= n; i++)
            {
                //get the factorial of i
                factorial = 1;
                for (int j = 1; j <= i; j++) factorial = factorial * j;

                //get the sum
                if (i % 2 == 1) sum = sum + ((float)i / factorial);
                else sum = sum - ((float)i / factorial);
            }

            sum = sum + 1;
            Console.WriteLine("\n\nThe summation is: {0}", sum);

            Console.ReadKey();
        }
    }
}