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;
import java.math.BigInteger;

public class Main {  
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    BigInteger[] A = new BigInteger[N];
    for (int i =0; i<N; i++) {
      A[i] = sc.nextBigInteger();
    }
    Arrays.sort(A);
    BigInteger a = BigInteger.ZERO;
    BigInteger b = BigInteger.ZERO;
    int p = 100001;
    for (int i =N-1; i>0; i--) {
      if (A[i].equals(A[i-1])) {
        a = A[i];
        p = i;
        break;
      }
    }
    for (int i =N-1; i>0; i--) {
      if (i != p && i != p-1 && A[i].equals(A[i-1])) {
        b = A[i];
        break;
      }
    }
    System.out.println(a.multiply(b));  
  }
}