Calculate Sum With Accuracy

/*
 * Write a program to calculate the sum (with accuracy of 0.001): 1 + 1/2 - 1/3 + 1/4 - 1/5 + ...
*/

using System;

class CalculateSumWithAccuracy
{
    static void Main()
    {
        decimal numbersSum=1m;
        decimal numbersSumOld = 0m;
        decimal difference = 1m;
        decimal i = 2m;

        while (difference >= 0.001m)
        {
            if (i % 2 == 0)
            {
                numbersSum += 1 / i;
                difference = Math.Abs(numbersSum - numbersSumOld);
                numbersSumOld = numbersSum;
            }
            else
            {
                numbersSum -= 1 / i;
                difference = Math.Abs(numbersSum - numbersSumOld);
                numbersSumOld = numbersSum;
            }
            i++;
        }
        Console.WriteLine("{0:0.000}", numbersSum);
    }
}