#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;

int main() {
  int n;
  cin >> n;
  vector<ll> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.rbegin(), v.rend());

  vector<ll> h;
  for (int i = 0; i < n; i++) {
    if (v[i] == v[i + 1]) {
      h.push_back(v[i]);
      i++;
    }
  }

  if (h.size() < 2) {
    cout << 0 << endl;
    return 0;
  }
  cout << (ll)h[0] * h[1] << endl;
}

### Prompt

Please create a solution in CPP to the following problem:

We have N sticks with negligible thickness. The length of the i-th stick is A_i.

Snuke wants to select four different sticks from these sticks and form a rectangle (including a square), using the sticks as its sides. Find the maximum possible area of the rectangle.

Constraints

* 4 \leq N \leq 10^5
* 1 \leq A_i \leq 10^9
* A_i is an integer.

Input

Input is given from Standard Input in the following format:


N
A_1 A_2 ... A_N


Output

Print the maximum possible area of the rectangle. If no rectangle can be formed, print 0.

Examples

Input

6
3 1 2 4 2 1


Output

2


Input

4
1 2 3 4


Output

0


Input

10
3 3 3 3 4 4 4 5 5 5


Output

20

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;

int main() {
  int n;
  cin >> n;
  vector<ll> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.rbegin(), v.rend());

  vector<ll> h;
  for (int i = 0; i < n; i++) {
    if (v[i] == v[i + 1]) {
      h.push_back(v[i]);
      i++;
    }
  }

  if (h.size() < 2) {
    cout << 0 << endl;
    return 0;
  }
  cout << (ll)h[0] * h[1] << endl;
}

```