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<vector>
#include<algorithm>
using namespace std;
int main(){
  int n;
  long ans=0;
  bool f=false;
  cin>>n;
  vector<int>a(n);
  for(int i=0;i<n;i++)cin>>a[i];
  sort(a.begin(),a.end());
  for(int i=n-1;i>0;i--){
    if(a[i-1]==a[i]){
      if(ans){cout<<ans*a[i]<<endl;return 0;}
      ans=a[i--];
    }
  }
  cout<<ans<<endl;
  return 0;
}