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 <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int N;
  cin >> N;
  map<int, int> mp;
  vector<int> t;
  for (int i = 0; i < N; i++) {
    int a;
    cin >> a;
    mp[a]++;
    if (mp[a] == 2) {
      mp[a] = 0;
      t.push_back(a);
    }
  }
  sort(t.begin(), t.end(), greater<int>());
  cout << (t.size() >= 2 ? 1LL * t[0] * t[1] : 0) << '\n';
  return 0;
}
