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;
  set<int> s;
  vector<int> v;
  for (int i=0;i<N;i++){
    int x;
    cin >> x;
    if (!s.count(x)){
      s.insert(x);
    }
    else {
      v.push_back(x);
      s.erase(x);
    }
  }
  sort(v.begin(),v.end());
  int l=v.size();
  if (l>=2){
    cout << (long long)v[l-1]*v[l-2] << endl;
  }
  else {
    cout << 0 << endl;
  }
}