#include <bits/stdc++.h>
using namespace std;
using ll = long long;
// const ll MOD = 1e9+7;

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

	int n; cin >> n;
    vector<array<ll, 2>> dp(n+1);
    dp[1] = {0, 1}; dp[2] = {2, 2};
    for (int i = 3; i <= n; i++) {
    	dp[i][0] = dp[i-1][0] + dp[i-2][1] * 2;
    	dp[i][1] = dp[i-1][0] + dp[i-1][1] + dp[i-2][1];
    }

	cout << dp[n][1] << "\n";
	
    return 0;
}