using System;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using static System.Math;
using LayoutKind = System.Runtime.InteropServices.LayoutKind;
using Debug = System.Diagnostics.Debug;
using StructLayoutAttribute = System.Runtime.InteropServices.StructLayoutAttribute;
using FieldOffsetAttribute = System.Runtime.InteropServices.FieldOffsetAttribute;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;
using System.Runtime.CompilerServices;

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