using System;
using System.Collections.Generic;

class Recursion
{
    static void Main()
    {
        Console.WriteLine("Please input n");
        int n = int.Parse(Console.ReadLine());
        Console.WriteLine(Fib(n));

    }

    static long Fib(int n)
    {
        if (n <2)
        {
            if (n == 1)
            {
                return 1;
            }
            if (n==0)
            {
                return 0;
            }

        }
        return Fib(n - 1) + Fib(n - 2);
    }

}