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;

long long n;
map<long long, int> mp;
vector<long long> v;

int main() {
  cin >> n;
  for(int i = 0; i < n; ++i) {
    long long a;
    cin >> a;
    ++mp[a];
    if(mp[a] == 2) {
      mp[a] = 0;
      v.push_back(a);
    }
  }
  sort(v.begin(), v.end(), greater<long long>());
  if(v.size() < 2)
    cout << 0 << endl;
  else {
    cout << v[0] * v[1] << endl;
  }
  return 0;
}