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++)
using namespace std;

signed main(void)
{
	int n; cin >> n;
	map<long long, long long> m;
	long long x, y;

	rep(i, n)
	{
		long long a;
		cin >> a;
		m[a]++;
	}
	x = y = 0;
	for (auto p : m)
	{
		auto k = p.first;
		auto v = p.second;
		if (v >= 2)
		{
			if (x < k)
			{
				y = x;
				x = k;
			}
		}
		if (v >= 4)
			y = x;
	}
	cout << x * y << endl;
}
