#include<bits/stdc++.h>

using namespace std;
using ll = long long;

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