import java.io.*;
import java.util.*;

public class delivery_mb {
    private static int[] read(int n, String line) {
        int[] data = new int[n];
        StringTokenizer st = new StringTokenizer(line);
        for (int i = 0; i < n; ++i) {
            data[i] = Integer.parseInt(st.nextToken());
        }
        return data;
    }

    private static long solve(int[] sorted) {
        int n = sorted.length;
        int k = n / 3;
        long result = 0;
        for (int i = 0, j = n; i < k; ++i) {
            --j;
            result += sorted[--j];
        }
        return result;
    }

    public static void main(String[] args) throws IOException {
        try (BufferedReader in = new BufferedReader(new InputStreamReader(System.in))) {
            int n = Integer.parseInt(in.readLine());
            int[] data = read(n, in.readLine());
            Arrays.sort(data);
            System.out.println(solve(data));
        }
    }
}