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
import java.util.Scanner;
import java.util.Arrays;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt(), tmp = 0;
		long A[] = new long[N], ans = 0;
		for (int i = 0; i < N; ++i) A[i] = sc.nextLong();
		sc.close();
		Arrays.sort(A);
		for (int i = N - 1; i > 0 && tmp != 2; --i) {
			if (A[i - 1] == A[i]) {
				if (tmp == 0) {
					ans = A[i];
					tmp = 1;
				}
				else {
					ans *= A[i];
					tmp = 2;
				}
				--i;
			}
		}
		if (tmp == 2) System.out.print(ans);
		else System.out.print(0);
	}
}