#include <iostream>
#include <algorithm>
#define int long long
using namespace std;

int n;
int a[200000];

signed main() {
	int i;
	
	cin >> n;
	for (i = 0; i < 2 * n; i++) cin >> a[i];
	sort(a, a + 2 * n);
	
	int ans = 0;
	for (i = 0; i < n; i++) {
		ans += a[2 * i] * a[2 * i + 1];
	}
	cout << ans << endl;
	return 0;
}