#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,m,n) for(int i=m; i<n; ++i)
#define repl(i,m,n) for(ll i=m; i<n; ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()

int main(){
    int N;
    cin >> N;
    vector<ll> A(2*N);
    rep(i, 0, 2*N) cin >> A[i];

    sort(all(A));

    ll ans = 0LL;
    for(int i = 0; i < 2*N; i += 2){
        ans += A[i]*A[i+1];
    }
    cout << ans << endl;

    return 0;
}