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;
#define ll long long
int main(){
  ll n,a;
  vector<ll> v;
  set<ll> s;
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>a;
   	if(s.find(a)==s.end()){
      s.insert(a);
    }else{
      v.push_back(-a);
      s.erase(a);
    }
  }
  sort(v.begin(),v.end());
  cout<<(v.size()>=2?v[0]*v[1]:0)<<endl;
  return 0;
}