Need code for fibanocci recursive

hi buddy,
You need recursive PROGRAM or a simple program without recursive function.

I write my code like this. Can any one tell the changes to be made in this. How can i do it with out using 3rd variable..
using System;

using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
{

    class fab
    {
        public static int fibonacci(int n)
        {
            int previous = -1;
            int next = 1;
            for (int i = 0; i < n; i++)
            {
                int sum = next + previous;
                //previous =  next+previous;
               // previous = previous + next;
                //next =  next-previous;
                //previous = next - previous;
                previous = next;
                next = sum;
                Console.WriteLine(next);

            }
            return next;
        }


        static void Main(string[] a)
        {
            int num;
            Console.WriteLine("Enter a number:");
            num = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("\n");
            Console.WriteLine("The first " + num + " number(s) in the fibonacci series are: ");
            fibonacci(num);

            Console.Read();
        }
    }

}