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.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Main {
    private static java.util.Scanner scanner = new java.util.Scanner(System.in);

    public static void main(String[] args) {
        int n = scanner.nextInt();
        List<Long> list = IntStream.range(0, n)
                .map(i -> scanner.nextInt())
                .boxed()
                .collect(Collectors.groupingBy(i -> i, Collectors.reducing(0, e -> 1, Integer::sum)))
                .entrySet().stream()
                .flatMapToLong(entry -> IntStream.range(0, entry.getValue() / 2).mapToLong(i -> entry.getKey()))
                .boxed()
                .sorted(Comparator.reverseOrder())
                .collect(Collectors.toList());

        System.out.println(list.size() < 2 ? 0 : list.get(0) * list.get(1));
    }
}