#include <bits/stdc++.h>
#define NMAX 15000008

using namespace std;
ifstream fin ("12perm.in");
ofstream fout ("12perm.out");

long long n, nr, dp[NMAX];

int main()
{
    fin >> n;
    dp[1] = 1;
    dp[2] = 2;
    dp[3] = 6;
    dp[4] = 12;
    dp[5] = 20;
    dp[6] = 34;
    for (int i = 7; i <= n; i++)
    {
        dp[i] = dp[i-1] + dp[i-2] - dp[i-5] + 4;
    }
    fout << dp[n];
    return 0;
}