package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"
)

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Buffer(make([]byte, 0, 200000*7+2), 200000*7+2)

	sc.Scan()
	N, _ := strconv.Atoi(sc.Text())
	sc.Scan()
	ss := strings.Fields(sc.Text())
	A := make([]int, 2*N)
	for i, s := range ss {
		A[i], _ = strconv.Atoi(s)
	}

	sort.Slice(A, func(i, j int) bool { return A[i] < A[j] })

	sum := 0
	for i := 0; i < 2*N; i += 2 {
		sum += A[i] * A[i+1]
	}

	fmt.Println(sum)
}