#include<bits/stdc++.h>
using namespace std;
using ll=long long;
int main(void){
  int n;
  cin>>n;
  map<int,int> m;
  for(int i=0;i<n;i++){
    int a;
    cin>>a;
    m[a]++;
  }
  ll n1=0,n2=0;
  for(auto i:m){
    if(i.second>=4){
      n1=i.first,n2=i.first;
    }else if(i.second>=2){
      swap(n1,n2);
      n1=i.first;
    }
  }
  cout<<n1*n2<<endl;
  return 0;
}
### Prompt

Create a solution in Cpp for the following problem:

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

### Response

```cpp
#include<bits/stdc++.h>
using namespace std;
using ll=long long;
int main(void){
  int n;
  cin>>n;
  map<int,int> m;
  for(int i=0;i<n;i++){
    int a;
    cin>>a;
    m[a]++;
  }
  ll n1=0,n2=0;
  for(auto i:m){
    if(i.second>=4){
      n1=i.first,n2=i.first;
    }else if(i.second>=2){
      swap(n1,n2);
      n1=i.first;
    }
  }
  cout<<n1*n2<<endl;
  return 0;
}
```