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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        long[] arr = new long[n * 2];
        for (int i = 0; i < n * 2; i++) {
            arr[i] = sc.nextInt();
        }
        Arrays.sort(arr);
        long ans = 0;
        for (int i = 0; i < n * 2; i += 2) {
            ans += arr[i] * arr[i + 1];
        }
        System.out.println(ans);
    }
}


class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}