#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
#include <climits>
using namespace std;

using ll = long long;
const int MOD = 1e9 + 7;

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

    int n;
    cin >> n;
    vector<int> dp1(n+1), dp0(n+1);
    dp0[0] = 1;
    dp0[1] = 1;
    for(int i = 2; i <= n; i++) {
        dp0[i] = 2*dp1[i-1] + dp0[i-1] + dp0[i-2];
        dp1[i] = dp0[i-2] + dp1[i-1];
    }
    cout << dp0[n] << "\n";
    return 0;
}