#include <bits/stdc++.h>

using namespace std;

using ll = long long;

template <class T>
T smax(T & x, T y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}

template <class T>
T smin(T & x, T y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}

int check(int n, int x, int y) {
    vector<int> a(n);
    vector<int> b(n);
    for (int i = 0; i < n; ++i) {
        a[i] = x % 3;
        b[i] = y % 3;
        x /= 3;
        y /= 3;
    }
    int ans = 0;
    for (int i = 0; i < n - 1; ++i) {
        if (a[i] == 0 && a[i + 1] == 1 && b[i + 1] == 2) {
            ans++;
        }
    }
    return ans;
}

void solveSlow() {
    int n;
    cin >> n;
    int pow = 1;
    for (int i = 0; i < n; ++i) {
        pow *= 3;
    }
    vector<vector<int>> a(pow, vector<int>(pow));
    for (int x = 0; x < pow; ++x) {
        for (int y = 0; y < pow; ++y) {
            a[x][y] = check(n, x, y);
        }
    }
    vector<vector<int>> dp(n, vector<int>(pow, 0));
    for (int i = 1; i < n; ++i) {
        for (int x = 0; x < pow; ++x) {
            for (int y = 0; y < pow; ++y) {
                smax(dp[i][y], dp[i - 1][x] + a[x][y]);
            }
        }
    }
    int mx = 0;
    for (int i = 0; i < pow; ++i) {
        smax(mx, dp[n - 1][i]);
    }
    cout << mx << endl;
}

void solve() {
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());
    ll ans = 0;
    for (int i = 0; i < n / 3; ++i) {
        ans += a[n - 2 - i * 2];
    }
    cout << ans << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
//    cin >> t;
    cout << fixed << setprecision(14);
    while (t--) {
        solve();
    }
//    cerr << clock() * 1.0 / CLOCKS_PER_SEC << "\n";
    return 0;
}