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;


int main(){
  long long N; cin>>N;
  std::set<long long> s;

  long long no1=0,no2=0;

  for(long long i=0;i<N;i++){
    long long k; cin>>k;
    auto result = s.insert(k);
    if(!result.second){
      if(no1<k){
        no2 = no1;
        no1 = k;
      }else if(no2<k){
        no2 = k;
      }
      s.erase(result.first);
    }

    cout<<endl;
  }

  cout<<no1*no2<<endl;
}
