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;

long n;
set<long long> s;

int main(){
  cin >> n;
  long long first = 0, second = 0;
  
  for(long i=0;i<n;i++){
    long long a;
    cin >> a;
    if(s.find(a) == s.end()){
      s.insert(a);
    }else{
      s.erase(s.find(a));
      if(a > first){
	second = first;
	first = a;
      }else if(a > second){
	second = a;
      }
    }
  }

  cout << first * second << endl;
}