#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pll = pair<ll,ll>;
using vll = vector<ll>;
using vi = vector<int>;
using pi = pair<int, int>;
using vpi = vector<pair<int, int>>;
using vai = vector<array<int, 3>>;

#define x first
#define y second
#define all(x) x.begin(), x.end()

void solve() {
    int n; cin >> n;
    vector<pll> dp(n+3);
    dp[0].x = 1;
    for (int i = 0; i < n; i++) {
        dp[i+1].x += dp[i].x;
        dp[i+1].y += dp[i].y;
        dp[i+1].y += dp[i].x*2;
        dp[i+2].x += dp[i].y;
        dp[i+2].x += dp[i].x;
    } cout << dp[n].x;
}

int main() {
	ios::sync_with_stdio(0);
    cin.tie(0);

    int t=1;
    //cin >> t;
    while (t--) {
        solve();
    }
}