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() {
  int N;
  cin >> N;
  map<int, int> m;
  vector<int> v;
  for (int i = 0; i < N; i++) {
    int a;
    cin >> a;
    m[a]++;
    if (m[a] % 2 == 0) v.push_back(a);
  }
  if (v.size() < 2) {
    cout << 0 << endl;
    return 0;
  }
  sort(v.rbegin(), v.rend());
  long long ans = (long long)v[0] * v[1];
  cout << ans << endl;

  return 0;
}
/* vim:set fdm=marker: */
