#include <bits/stdc++.h>
#include <assert.h>
using namespace std;
const long long MOD1 = 1000000007;
const long long MOD2 = 998244353;
#define logn long
#define lnog long
#define lgon long
#define itn int
typedef long long ll;
typedef pair<long long, long long> P;
const long long INF = 1e18;
int main(){
    long long N; cin >> N;
    vector<long long>A(2 * N); 
    for (long long i = 0; i < 2 * N; i++) {
        cin >> A[i];
    }
    sort(A.begin(), A.end(), greater<long long>());
    long long ans = 0;
    for (long long i = 0; i < N; i++) {
        ans += A[2*i]*A[2*i+1];
    }
    cout << ans << endl;
}