#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
    int N;
    int dp[1000001][4];

    cin >> N;

    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < 4; i++)
        {
            for (int k = 1; k < 4; k++)
            {
                if (k != j)
                    dp[i + k][k] += dp[i][j];
            }
        }
    }

    int ans = 0;
    for (int i = 0; i < 4; i++)
        ans += dp[N][i];

    cout << ans << endl;
    return 0;
}