import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

// INFO

class Task {
    public void solve(int testNumber, InputReader in, PrintWriter out) {
        int n = in.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; ++i) {
            a[i] = in.nextInt();
        }
        long[] sum = new long[n * (n - 1) / 2];
        int cnt = 0;
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < i; ++j) {
                sum[cnt++] = a[i] + a[j];
            }
        }
        Arrays.sort(sum);
        long ret = sum[0];
        for (int k = 1; k < n * (n - 1) / 2; ++k) {
            if (sum[k] != sum[k - 1]) {
                ret += sum[k];
            }
        }
        out.println(ret);
    }
}

public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));

        Task solver = new Task();
        while (in.hasMoreTokens()) {
            solver.solve(1, in, out);
        }
        out.close();
    }
}

class InputReader {
    BufferedReader br;
    StringTokenizer st;

    public InputReader(File f) {
        try {
            br = new BufferedReader(new FileReader(f));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    public InputReader(InputStream f) {
        br = new BufferedReader(new InputStreamReader(f));
    }

    String next() {
        while (st == null || !st.hasMoreTokens()) {
            String s = null;
            try {
                s = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (s == null)
                return null;
            st = new StringTokenizer(s);
        }
        return st.nextToken();
    }

    boolean hasMoreTokens() {
        while (st == null || !st.hasMoreTokens()) {
            String s = null;
            try {
                s = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (s == null)
                return false;
            st = new StringTokenizer(s);
        }
        return true;
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }
}