using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine ("Enter Fibonachi Index");

        int index = Int32.Parse(Console.ReadLine());

        bool finished = false; // siamti = LO

        int counter = 2;

        int answer = 0;

        int one_before = 1;

        int two_before = 1;

        while (!finished) // kol od LO siiamti

        {

            if ( index == 1 || index == 2 )

            {

                finished = true;

                answer = 1;

            }

            else

            {

                int next = one_before + two_before;

                two_before = one_before;

                one_before = next;

                counter++;

                if (counter == index)

                {

                    finished = true;

                    answer = one_before;

                }

            }

        }

        Console.WriteLine("answer is {0}", answer);

    }

}