// jarda-L.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <queue>

#define ll long long
using namespace std;

ll n;
int main()
{
    cin >> n;
    vector<ll>dp(n + 1, 0);
    dp[0] = 1;
    dp[1] = 1;
    dp[2] = 2;
    dp[3] = 5;
    if (n <= 3)
    {
        cout << dp[n];
        return 0;
    }
    for (int i = 4; i <= n; ++i)
    {
        dp[i] = dp[i - 1] + dp[i - 2];
        int j = i - 3;
        while (j>=0)
        {
            dp[i] += 2 * dp[j];
            --j;
        }
    }
   //for (auto& e : dp)cout << e << " ";
    cout << dp[n];
    return 0;
}

// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu

// Tips for Getting Started: 
//   1. Use the Solution Explorer window to add/manage files
//   2. Use the Team Explorer window to connect to source control
//   3. Use the Output window to see build output and other messages
//   4. Use the Error List window to view errors
//   5. Go to Project > Add New Item to create new code files, or Project > Add Existing Item to add existing code files to the project
//   6. In the future, to open this project again, go to File > Open > Project and select the .sln file