Fibonacci Numbers

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

namespace _10.FibonacciNumbers
{
    class FibonacciNumbers
    {
        static void Main()
        {
            Console.WriteLine("Enter a number N for range: ");
            BigInteger n = BigInteger.Parse(Console.ReadLine());
            BigInteger firstNum = 0;
            BigInteger secondNum = 1;
            BigInteger thirdNum = 1;
            for (int i = 0; i < n; i++)
            {
                thirdNum = secondNum;
                secondNum = firstNum + secondNum;
                firstNum = thirdNum;
                Console.Write(firstNum + " ");
            }
            Console.ReadLine();
        }
    }
}