using System;

public class Program

{

    public static void Main()

    {

        string input;

        int inputNumber;

        int firstNumber=0;

        int secondNumber =1;

        int sumOfPreviousNumber=0;

        Console.WriteLine("Fibonacci Freeze");

        Console.Write("Enter a number: ");

        input = Console.ReadLine();

        if(Int32.TryParse(input, out inputNumber)== true)

        {

            if(inputNumber <= 0)

            {

                Console.WriteLine("Zero or negative input is not allowed.");

            }

            else 

            {

                int number = 1;

                while (number < inputNumber)

                {

                    sumOfPreviousNumber = firstNumber + secondNumber;

                    firstNumber = secondNumber;

                    secondNumber = sumOfPreviousNumber;

                    number++;

                }

                Console.WriteLine("The fibonacci freeze is {0:#,0}.",sumOfPreviousNumber );

            }

        }

    }

}