#include<bits/stdc++.h>
#include <atcoder/all>
#ifdef LOCAL
#include <debug_print.hpp>
#define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...) (static_cast<void>(0))
#endif
using namespace atcoder;
using mint=modint998244353;
using namespace std;
using ll=long long;
using ul=unsigned long long;
int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1};
int dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};
using Graph=vector<vector<int>>;
int op(ll a,ll b){return int(a+b);}
int e(){return 0;}
int main(){
    ll N;
    cin>>N;
    vector<ll>A(2*N);
    for(int i=0;i<2*N;i++)cin>>A[i];
    sort(A.rbegin(),A.rend());
    ll ans=0;
    for(int i=0;i<N;i++)ans+=A[2*i]*A[2*i+1];
    cout<<ans<<endl;
}