using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(CountWay(9));

    }

    static int CountWay(int n)

    {

        if(n <= 2) return n;

        int a = 1, b= 2;

        for(int i = 3; i <= n; i++)

        {

            b = a + b;

            a = b - a;

        }

        return b;

    }

}