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;

using LL = long long;

int main() {
  int N;
  cin >> N;

  map<LL, int> cnt;
  vector<LL> v = {0, 0};
  for(auto i=0; i<N; ++i) {
    LL A;
    cin >> A;
    ++cnt[A];
    if(cnt[A]==2||cnt[A]==4) v.emplace_back(A);
  }
  sort(begin(v), end(v), greater<LL>());

  cout << v[0]*v[1] << endl;
}
