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
#include <iostream>
#include <set>

using namespace std;

int main() {
  long long N, L[2]{};
  cin >> N;
  set<int> S;
  while (cin >> N) {
    if (!S.insert(N).second) {
      S.erase(N);
      if (N > L[0]) L[1] = L[0], L[0] = N;
      else if (N > L[1]) L[1] = N;
    }
  }
  cout << L[0] * L[1] << endl;
}
