using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;


class Magatoro {
    
    static void Main() {
        int N = int.Parse(Console.ReadLine());
        long[] A = new long[N+1];
        A[0] = 1;
        A[1] = 1;
        for(int i = 2; i <= N; i++) {
            A[i] = A[i - 1] + A[i - 2];
        }
        Console.WriteLine(A[N]);
    }
}