using System;

using System.IO;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter number");

        int number = Convert.ToInt16(Console.ReadLine());

        if (number > 2)

        {

            int fibonacci = (number-1)+(number-2);

            Console.WriteLine(fibonacci);

        }

        else

        {

            Console.WriteLine("1");

        }

    }

}