// Járda I és L alakú járólapokkal.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <vector>

using namespace std;

int i;

int main()
{
    cin >> n;
    vector <unsigned long long> x(n + 1);

    x[0] = 1;
    x[1] = 1;
    x[2] = 2;
    x[3] = 5;
    for (i = 1; i <= n; ++i)
    {
        x[i] = x[i - 1] + x[i - 2];
        for (int j = 0; j <= i-3; ++j)
        {
            x[i] += x[j];
        }
    }

    cout << x[n];
}

// 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