#include<bits/stdc++.h>
#include<iostream>
using namespace std;
using LL = long long;
using P = pair<int,int>;
using Graph = vector<vector<int>>;
const int INF = 1 << 29;
const long long LINF = 1LL << 60;
#define all(x) (x).begin(), (x).end()
#define rep(i,n) for(int i = 0; i < (n); ++i)
template<class T>void chmin(T&a, T b){if(a > b) a = b;}
template<class T>void chmax(T&a, T b){if(a < b) a = b;}


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