#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N;
	cin >> N;
	vector<long long> A( N * 2 );
	for( int i = 0; i < N * 2; i++ ) {
		cin >> A[i];
	}

	sort( A.begin(), A.end() );
	long long ans = 0;
	for( int i = 0; i < N; i++ ) {
		ans += A[i * 2] * A[i * 2 + 1];
	}

	cout << ans << endl;
}