using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Fibonacci
{
    static void Main(string[] args)
    {
        int n = int.Parse(Console.ReadLine());
        int first = 1;
        int second = 1;
        for (int i = 0; i < n - 1; i++)
        {
            int third = first + second;
            first = second;
            second = third;
        }
        Console.WriteLine(second);
    }
}