import java.util.*;
import java.io.*;
import java.math.*;
import java.util.stream.Stream;

public class Main{
    /* 入出力 */
    static BufferedReader buff = new BufferedReader(new InputStreamReader(System.in));
    static StringTokenizer st;
    static PrintWriter output = new PrintWriter(System.out);
    static Scanner sc = new Scanner(System.in);
    /* 定数 */
    static final int [] y4 = {0,1,0,-1};
    static final int [] x4 = {1,0,-1,0};
    static final int  INF1 = Integer.MAX_VALUE;
    static final long INF2 = Long.MAX_VALUE;
    static final long MOD1 = (long)1e9+7;
    static final long MOD2 = 998244353;
    /* Main */
    public static void main(String[] args) throws IOException{
        int n = sc.nextInt();
        int [] A = new int[2*n];
        for(int i=0;i<2*n;i++) A[i] = sc.nextInt();
        Arrays.sort(A);
        long ans = 0;
        for(int i=0;i<n;i++) {
            ans += (long)A[2*i]*A[(2*i)+1];
        }
        output.print(ans);
        output.flush();
    }
}