using System;

public class Program

{

    public static void Main()

    {

    int n = Convert.ToInt32(Console.ReadLine());    

    int i = 0;

    int sec = 0;

    int last = 1;

    for (int j = 0; i < 10; i++)

    {

    }

    while (i < (n-2))

    {

        int newNumber = sec + last;

        sec = last;

        last = newNumber;

        i++;

    }

        Console.WriteLine(last);

    }

}