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;
int main(){
	int N,i,x;
	long long int y=0,z=0;
	set<long long int>A;
	vector<long long int>B;
	scanf("%d",&N);
	for(i=0;i<N;i++){
		scanf("%d",&x);
		if(A.find(x)!=A.end()){
			B.push_back(x);
			A.erase(x);		}
		else A.insert(x);
	}
	sort(B.begin(),B.end());
	if(B.size()>=2) printf("%lld",B[B.size()-1]*B[B.size()-2]);
	else printf("0");
}