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;
typedef long long ll;

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