#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)

int main(){
    int N;
    cin >> N;

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

    sort(A.begin(), A.end());

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

    return 0;
}