#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int N, A[202020];
ll sum = 0;

int main() {
  cin >> N;
  for (int i = 1; i <= 2 * N; i++) cin >> A[i];
  sort(A + 1, A + 2 * N + 1);
  for (int i = 1; i <= N; i++) {
    sum += (ll)A[2 * i - 1] * A[2 * i];
  }
  cout << sum << endl;
  return 0;
}