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 rep(i,n) for(int i=0;i<(n);i++)
#define all(x) (x).begin(),(x).end()
#define ll long long
int main(){
  int N;
  cin>>N;
  vector<ll> A(N);
  rep(i,N) cin>>A[i];
  sort(all(A));
  ll ans=1,c=0,x=1;
  rep(i,N){
    if(x&&A[N-1-i]==A[N-2-i]){
      ans*=A[N-1-i];
      c++;
      x=0;
    }else x=1;
    if(c==2) break;
  }
  cout<<(c==2?ans:0)<<endl;
}