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

namespace ConsoleApplication6
{
    class Program
    {
        public static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());

            long[] row = new long[N+1];

            row[0] = 1;
            row[1] = 1;

            for (int i = 2; i < N+1; i++)
            {
                row[i] = row[i - 1] + row[i - 2];
            }

            Console.WriteLine(row[N]);
        }
    }
}