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 <algorithm>
using namespace std;

typedef long long ll;

int main() {
  int N;
  cin >> N;
  ll a[N];
  for (int i = 0; i < N; i++) cin >> a[i];

  sort(a, a + N);
  ll x = 0, y = 0;
  for (int i = N - 1; i > 0; i--) {
    if (a[i] == a[i-1]) {
      if (x == 0) x = a[i];
      else if (y == 0) y = a[i];
      i--;
    }
  }

  cout << x * y << endl;

  return 0;
}
