#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1e9+7;
int main(){
    int N,A[100000];
    cin >> N;
    for(int i = 0;i < N;i++)cin >> A[i];
    sort(A,A+N,greater<int>());
    ll a[2] = {};
    for(int i = 0,idx = 0;i < N-1;i++){
        if(A[i] == A[i+1]){
            a[idx++] = A[i];
            i++;
        }
    }
    cout << a[0] * a[1] << endl;
}
### Prompt

Please create a solution in CPP 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>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1e9+7;
int main(){
    int N,A[100000];
    cin >> N;
    for(int i = 0;i < N;i++)cin >> A[i];
    sort(A,A+N,greater<int>());
    ll a[2] = {};
    for(int i = 0,idx = 0;i < N-1;i++){
        if(A[i] == A[i+1]){
            a[idx++] = A[i];
            i++;
        }
    }
    cout << a[0] * a[1] << endl;
}
```