using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
using System.Runtime.Intrinsics.Arm;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var dp = new long[n + 1];
        dp[0] = 1;
        dp[1] = 1;
        for (var i = 2; i <= n; ++i) dp[i] = dp[i - 1] + dp[i - 2];
        WriteLine(dp[n]);
    }
}