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;

int main(){
    size_t N;
    cin >> N;
    map<unsigned long, unsigned long> a;
    unsigned long ans0{0}, ans1{0};
    for(unsigned long i = 0, A; i < N; ++i){
        cin >> A;
        if(++a[A] == 2){
            a[A] = 0;
            if(ans0 < A)swap(ans0, A);
            if(ans1 < A)swap(ans1, A);
        }
    }
    cout << ans0 * ans1 << endl;
}