#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int n;
    cin >> n;
    long long a[n];
    for(int i = 0; i < n; i++){
        cin >> a[i];
    }
    sort(a,a+n);
    unsigned long long  p = 0,q = 0;
    for(int i = 1;i < n; i++ ){
        if(a[i-1] == a[i]){
            p = q;
            q = a[i];
            a[i-1] = 0;
            a[i] = 0;
        }
    }
    cout << p*q << endl;

    return 0;
}
### Prompt

Your challenge is to write a CPP solution to 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;
 
int main(){
    int n;
    cin >> n;
    long long a[n];
    for(int i = 0; i < n; i++){
        cin >> a[i];
    }
    sort(a,a+n);
    unsigned long long  p = 0,q = 0;
    for(int i = 1;i < n; i++ ){
        if(a[i-1] == a[i]){
            p = q;
            q = a[i];
            a[i-1] = 0;
            a[i] = 0;
        }
    }
    cout << p*q << endl;

    return 0;
}
```