#include <iostream>
#include <fstream>
using namespace std;
ifstream in("12perm.in");
ofstream out("12perm.out");
const int maxn = 15000005;
int A[maxn];
int B[maxn];
int main()
{
    int n;
    in >> n;
    A[1] = 1;
    B[1] = 0;
    A[2] = 2;
    B[2] = 0;
    A[3] = 4;
    B[3] = 2;
    A[4] = 8;
    B[4] = 4;
    for(int i = 5; i <= n; i++)
    {
        A[i] = A[i - 1] + A[i - 3] + 2;
        B[i] = B[i - 1] + A[i - 2];
    }
    out << A[n] + B[n] << "\n";
    return 0;
}