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>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define all(v) v.begin(), v.end()
using namespace std;
typedef long long ll;

int main() {
	
	int n;
	cin >> n;
	vector<int> a(n);
	vector<int> pair;
	rep(i, n) cin >> a[i];
	sort(all(a));
	pair.push_back(0);
	pair.push_back(0);
	rep(i, n-1){
		if(a[i] == a[i+1]) pair.push_back(a[i]), i++;
	}
	cout << (ll) pair[pair.size()-1] * pair[pair.size()-2] << endl;
	return 0;
}